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18 tháng 5 2017

giải đc sao pn dễ mk

19 tháng 5 2017

chẳng ai giải, thôi mình giải vậy!

a) Đặt \(y=x^2+4x+8\),phương trình có dạng:

\(t^2+3x\cdot t+2x^2=0\)

\(\Leftrightarrow t^2+xt+2xt+2x^2=0\)

\(\Leftrightarrow t\left(t+x\right)+2x\left(t+x\right)=0\)

\(\Leftrightarrow\left(2x+t\right)\left(t+x\right)=0\)

\(\Leftrightarrow\left(2x+x^2+4x+8\right)\left(x^2+4x+8+x\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=-2\\x=-4\end{cases}}\)vậy tập nghiệm của phương trình là:S={-2;-4}

b) nhân 2 vế của phương trình với 12 ta được:

\(\left(6x+7\right)^2\left(6x+8\right)\left(6x+6\right)=72\)

Đặt y=6x+7, ta được:\(y^2\left(y+1\right)\left(y-1\right)=72\)

giải tiếp ra ta sẽ được S={-2/3;-5/3}

c) \(\left(x-2\right)^4+\left(x-6\right)^4=82\)

S={3;5}

d)s={1}

e) S={1;-2;-1/2}

f) phương trình vô nghiệm

Bài 1:

a) 5(x-3)-4=2(x-1)

\(\Leftrightarrow5x-15-4=2x-2\)

\(\Leftrightarrow5x-19-2x+2=0\)

\(\Leftrightarrow3x-17=0\)

\(\Leftrightarrow3x=17\)

\(\Leftrightarrow x=\frac{17}{3}\)

Vậy: \(x=\frac{17}{3}\)

b) 5-(6-x)=4(3-2x)

\(\Leftrightarrow5-6+x=12-8x\)

\(\Leftrightarrow-1+x-12+8x=0\)

\(\Leftrightarrow-13+9x=0\)

\(\Leftrightarrow9x=13\)

\(\Leftrightarrow x=\frac{13}{9}\)

Vậy: \(x=\frac{13}{9}\)

c) (3x+5)(2x+1)=(6x-2)(x-3)

\(\Leftrightarrow6x^2+3x+10x+5=6x^2-18x-2x+6\)

\(\Leftrightarrow6x^2+13x+5=6x^2-20x+6\)

\(\Leftrightarrow6x^2+13x+5-6x^2+20x-6=0\)

\(\Leftrightarrow33x-1=0\)

\(\Leftrightarrow33x=1\)

\(\Leftrightarrow x=\frac{1}{33}\)

Vậy: \(x=\frac{1}{33}\)

d) \(\left(x+2\right)^2+2\left(x-4\right)=\left(x-4\right)\left(x-2\right)\)

\(\Leftrightarrow x^2+4x+4+2x-8=x^2-2x-4x+8\)

\(\Leftrightarrow x^2+6x-4=x^2-6x+8\)

\(\Leftrightarrow x^2+6x-4-x^2+6x-8=0\)

\(\Leftrightarrow12x-12=0\)

\(\Leftrightarrow x=1\)

Vậy:x=1

Bài 2:

a)\(\frac{x}{3}-\frac{5x}{6}-\frac{15x}{12}=\frac{x}{4}-5\)

\(\Leftrightarrow\frac{x}{3}-\frac{5x}{6}-\frac{5x}{4}-\frac{x}{4}+5=0\)

\(\Leftrightarrow\frac{4x}{12}-\frac{10x}{12}-\frac{15x}{12}-\frac{3x}{12}+\frac{60}{12}=0\)

\(\Leftrightarrow4x-10x-15x-3x+60=0\)

\(\Leftrightarrow-24x+60=0\)

\(\Leftrightarrow-24x=-60\)

\(\Leftrightarrow x=\frac{5}{2}\)

Vậy: \(x=\frac{5}{2}\)

b) \(\frac{8x-3}{4}-\frac{3x-2}{2}=\frac{2x-1}{2}+\frac{x+3}{4}\)

\(\Leftrightarrow\frac{8x-3}{4}-\frac{3x-2}{2}-\frac{2x-1}{2}-\frac{x+3}{4}=0\)

\(\Leftrightarrow\frac{8x-3}{4}-\frac{2\left(3x-2\right)}{4}-\frac{2\left(2x-1\right)}{4}-\frac{x+3}{4}=0\)

\(\Leftrightarrow8x-3-2\left(3x-2\right)-2\left(2x-1\right)-\left(x+3\right)=0\)

\(\Leftrightarrow8x-3-6x+4-4x+2-x-3=0\)

\(\Leftrightarrow-3x=0\)

\(\Leftrightarrow x=0\)

Vậy: x=0

c) \(\frac{x-1}{2}-\frac{x+1}{15}-\frac{2x-13}{6}=0\)

\(\Leftrightarrow\frac{15\left(x-1\right)}{30}-\frac{2\left(x+1\right)}{30}-\frac{5\left(2x-13\right)}{30}=0\)

\(\Leftrightarrow15\left(x-1\right)-2\left(x+1\right)-5\left(2x-13\right)=0\)

\(\Leftrightarrow15x-15-2x-2-10x+65=0\)

\(\Leftrightarrow3x+48=0\)

\(\Leftrightarrow3x=-48\)

\(\Leftrightarrow x=-16\)

Vậy: x=-16

d) \(\frac{3\left(3-x\right)}{8}+\frac{2\left(5-x\right)}{3}=\frac{1-x}{2}-2\)

\(\Leftrightarrow\frac{3\left(3-x\right)}{8}+\frac{2\left(5-x\right)}{3}-\frac{1-x}{2}+2=0\)

\(\Leftrightarrow\frac{9\left(3-x\right)}{24}+\frac{16\left(5-x\right)}{24}-\frac{12\left(1-x\right)}{24}+\frac{48}{24}=0\)

\(\Leftrightarrow9\left(3-x\right)+16\left(5-x\right)-12\left(1-x\right)+48=0\)

\(\Leftrightarrow27-9x+80-16x-12+12x+48=0\)

\(\Leftrightarrow-13x+143=0\)

\(\Leftrightarrow-13x=-143\)

\(\Leftrightarrow x=11\)

Vậy: x=11

e) \(\frac{3\left(5x-2\right)}{4}-2=\frac{7x}{3}-5\left(x-7\right)\)

\(\Leftrightarrow\frac{3\left(5x-2\right)}{4}-2-\frac{7x}{3}+5\left(x-7\right)=0\)

\(\Leftrightarrow\frac{9\left(5x-2\right)}{12}-\frac{24}{12}-\frac{28x}{12}+\frac{60\left(x-7\right)}{12}=0\)

\(\Leftrightarrow9\left(5x-2\right)-24-28x+60\left(x-7\right)=0\)

\(\Leftrightarrow45x-18-24-28x+60x-420=0\)

\(\Leftrightarrow77x-462=0\)

\(\Leftrightarrow77x=462\)

\(\Leftrightarrow x=6\)

Vậy:x=6

Bài 3:

a) \(\left(5x-4\right)\left(4x+6\right)=0\)

\(\Leftrightarrow\left(5x-4\right)\cdot2\cdot\left(2x+3\right)=0\)

\(2\ne0\)

nên \(\left[{}\begin{matrix}5x-4=0\\2x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}5x=4\\2x=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{4}{5}\\x=\frac{-3}{2}\end{matrix}\right.\)

Vậy: \(x\in\left\{\frac{4}{5};-\frac{3}{2}\right\}\)

b) \(\left(x-5\right)\left(3-2x\right)\left(3x+4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\3-2x=0\\3x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\2x=3\\3x=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\frac{3}{2}\\x=\frac{-4}{3}\end{matrix}\right.\)

Vậy: \(x\in\left\{5;\frac{3}{2};\frac{-4}{3}\right\}\)

c) \(\left(2x+1\right)\left(x^2+2\right)=0\)

Ta có: \(\left(2x+1\right)\left(x^2+2\right)=0\)(1)

Ta có: \(x^2\ge0\forall x\)

\(\Rightarrow x^2+2\ge2\ne0\forall x\)(2)

Từ (1) và (2) suy ra:

\(2x+1=0\)

\(\Leftrightarrow2x=-1\)

\(\Leftrightarrow x=\frac{-1}{2}\)

Vậy: \(x=\frac{-1}{2}\)

d) \(\left(8x-4\right)\left(x^2+2x+2\right)=0\)

\(\Leftrightarrow4\left(2x-1\right)\left(x^2+2x+2\right)=0\)

Ta có: \(x^2+2x+2=x^2+2x+1+1=\left(x+1\right)^2+1\)

Ta lại có \(\left(x+1\right)^2\ge0\forall x\)

\(\Rightarrow\left(x+1\right)^2+1\ge1\ne0\forall x\)(3)

Ta có: \(4\ne0\)(4)

Từ (3) và (4) suy ra

2x-1=0

\(\Leftrightarrow2x=1\)

\(\Leftrightarrow x=\frac{1}{2}\)

Vậy: \(x=\frac{1}{2}\)

Bài 4:

a) \(\left(x-2\right)\left(2x+3\right)=\left(x-1\right)\left(x-2\right)\)

\(\Leftrightarrow2x^2+3x-4x-6=x^2-2x-x+2\)

\(\Leftrightarrow2x^2-x-6=x^2-3x+2\)

\(\Leftrightarrow2x^2-x-6-x^2+3x-2=0\)

\(\Leftrightarrow x^2+2x-8=0\)

\(\Leftrightarrow x^2+2x+1-9=0\)

\(\Leftrightarrow\left(x+1\right)^2-3^2=0\)

\(\Leftrightarrow\left(x+1-3\right)\left(x+1+3\right)=0\)

\(\Leftrightarrow\left(x-2\right)\left(x+4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)

Vậy: \(x\in\left\{2;-4\right\}\)

b) \(\left(2x+5\right)\left(x-4\right)=\left(x-5\right)\left(4-x\right)\)

\(\Leftrightarrow\left(2x+5\right)\left(x-4\right)-\left(x-5\right)\left(4-x\right)=0\)

\(\Leftrightarrow\left(2x+5\right)\left(x-4\right)+\left(x-5\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left(x-4\right)\left(2x+5+x-5\right)=0\)

\(\Leftrightarrow\left(x-4\right)\cdot3x=0\)

\(3\ne0\)

nên \(\left[{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

Vậy: \(x\in\left\{0;4\right\}\)

c) \(9x^2-1=\left(3x+1\right)\left(2x-3\right)\)

\(\Leftrightarrow\left(3x-1\right)\left(3x+1\right)-\left(3x+1\right)\left(2x-3\right)=0\)

\(\Leftrightarrow\left(3x+1\right)\left[\left(3x-1\right)-\left(2x-3\right)\right]=0\)

\(\Leftrightarrow\left(3x+1\right)\left(3x-1-2x+3\right)=0\)

\(\Leftrightarrow\left(3x+1\right)\left(x+2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}3x+1=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=-1\\x=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-1}{3}\\x=-2\end{matrix}\right.\)

Vậy: \(x\in\left\{-\frac{1}{3};-2\right\}\)

d) \(\left(x+2\right)^2=9\left(x^2-4x+4\right)\)

\(\Leftrightarrow x^2+4x+4-9\left(x^2-4x+4\right)=0\)

\(\Leftrightarrow x^2+4x+4-9x^2+36x-36=0\)

\(\Leftrightarrow-8x^2+40x-32=0\)

\(\Leftrightarrow-\left(8x^2-40x+32\right)=0\)

\(\Leftrightarrow-8\left(x^2-5x+4\right)=0\)

\(-8\ne0\)

nên \(x^2-5x+4=0\)

\(\Leftrightarrow x^2-x-4x+4=0\)

\(\Leftrightarrow x\left(x-1\right)-4\left(x-1\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=4\end{matrix}\right.\)

Vậy: \(x\in\left\{1;4\right\}\)

e) \(4\left(2x+7\right)^2-9\left(x+3\right)^2=0\)

\(\Leftrightarrow4\left(4x^2+28x+49\right)-9\left(x^2+6x+9\right)=0\)

\(\Leftrightarrow16x^2+112x+196-9x^2-54x-81=0\)

\(\Leftrightarrow7x^2+58x+115=0\)

\(\Leftrightarrow7x^2+23x+35x+115=0\)

\(\Leftrightarrow x\left(7x+23\right)+5\left(7x+23\right)=0\)

\(\Leftrightarrow\left(7x+23\right)\left(x+5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}7x+23=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}7x=-23\\x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-23}{7}\\x=-5\end{matrix}\right.\)

Vậy: \(x\in\left\{\frac{-23}{7};-5\right\}\)

Bài 5:

a) \(\left(9x^2-4\right)\left(x+1\right)=\left(3x+2\right)\left(x^2-1\right)\)

\(\Leftrightarrow\left(9x^2-4\right)\left(x+1\right)-\left(3x+2\right)\left(x^2-1\right)=0\)

\(\Leftrightarrow\left(3x-2\right)\left(3x+2\right)\left(x+1\right)-\left(3x+2\right)\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow\left(3x+2\right)\left(x+1\right)\left[\left(3x-2\right)-\left(x-1\right)\right]=0\)

\(\Leftrightarrow\left(3x+2\right)\left(x+1\right)\left(3x-2-x+1\right)=0\)

\(\Leftrightarrow\left(3x+2\right)\left(x+1\right)\left(2x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}3x+2=0\\x+1=0\\2x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=-2\\x=-1\\2x=1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-2}{3}\\x=-1\\x=\frac{1}{2}\end{matrix}\right.\)

Vậy: \(x\in\left\{-\frac{2}{3};-1;\frac{1}{2}\right\}\)

b) \(\left(x-1\right)^2-1+x^2=\left(1-x\right)\left(x+3\right)\)

\(\Leftrightarrow x^2-2x+1-1+x^2=x+3-x^2-3x\)

\(\Leftrightarrow2x^2-2x=-x^2-2x+3\)

\(\Leftrightarrow2x^2-2x+x^2+2x-3=0\)

\(\Leftrightarrow3x^2-3=0\)

\(\Leftrightarrow3\left(x^2-1\right)=0\)

\(\Leftrightarrow3\left(x-1\right)\left(x+1\right)=0\)

\(3\ne0\)

nên \(\left[{}\begin{matrix}x-1=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)

Vậy: \(x\in\left\{1;-1\right\}\)

c) \(x^4+x^3+x+1=0\)

\(\Leftrightarrow x^3\left(x+1\right)+\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x^3+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x+1\right)\left(x^2-x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)^2\cdot\left(x^2-x+1\right)=0\)(5)

Ta có: \(x^2-x+1=x^2-2\cdot x\cdot\frac{1}{2}+\frac{1}{4}-\frac{1}{4}+1=\left(x-\frac{1}{2}\right)^2+\frac{3}{4}\)

Ta lại có: \(\left(x-\frac{1}{2}\right)^2\ge0\forall x\)

\(\Rightarrow\left(x-\frac{1}{2}\right)^2+\frac{3}{4}\ge\frac{3}{4}\ne0\forall x\)(6)

Từ (5) và (6) suy ra

\(\left(x+1\right)^2=0\)

\(\Leftrightarrow x+1=0\)

\(\Leftrightarrow x=-1\)

Vậy: x=-1

18 tháng 2 2020

ko khó đâu, chủ yếu nhát làm

24 tháng 4 2023

`a,` \(\dfrac{5x+2}{6}-\dfrac{8x-1}{3}=\dfrac{4x+2}{5}-5\)

`<=> (5(5x+2))/30 - (10(8x-1))/30 = (6(4x+2))/30 - (5.30)/30`

`<=> 5(5x+2) - 10(8x-1) =6(4x+2) - 5.30`

`<=> 25x + 10 - 80x + 10 = 24x+12 - 150`

`<=> -55x +20 = 24x-138`

`<=> -55x -24x=-138-20`

`<=>-79x=-158`

`<=> x=2`

Vậy pt có nghiệm `x=2`

`b,` \(\dfrac{x+2}{x-2}-\dfrac{1}{x}=\dfrac{2}{x\left(x-2\right)}\)

ĐKXĐ : \(\left\{{}\begin{matrix}x-2\ne0\\x\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ne2\\x\ne0\end{matrix}\right.\)

Ta có : `(x+2)/(x-2) -1/x = 2/(x(x-2))`

`<=> (x(x+2))/(x(x-2)) - (x-2)/(x(x-2))  = 2/(x(x-2))`

`=> x^2 +2x - x +2 = 2`

`<=> x^2 + x =0`

`<=>x(x+1)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\left(l\right)\\x=-1\end{matrix}\right.\)

Vậy pt có nghiệm `x=-1`

`c,2x^3 + 6x^2 =x^2 +3x`

`<=> 2x^3 + 6x^2 -x^2 -3x=0`

`<=> 2x^3 + 5x^2 -3x=0`

`->` Đề có sai ko ạ ?

`d,` \(\left|x-4\right|+3x=5\) `(1)`

Thường hợp `1` : `x-4 >= 0<=> x >=0` thì phương trình `(1)` thở thành :

`x-4 = 5-3x`

`<=> x+3x=5+4`

`<=> 4x=9`

`<=> x= 9/4 (t//m)`

Trường hợp `2` : `x-4< 0<=> x<0` thì phương trình `(1)` trở thành :

`-(x-4) =5-3x`

`<=> -x +4=5-3x`

`<=> -x+3x=5-4`

`<=> 2x =1`

`<=>x=1/2 ( kt//m)`

Vậy phương trình có nghiệm `x=9/4`

 

 

24 tháng 4 2023

đây là phương trình mà đâu phải bất phương trình đâu

6 tháng 1 2022

đoán xem

4 tháng 3 2021

\(\frac{x^2-2x+2}{x-1}+\frac{x^2-8x+20}{x-4}=\frac{x^2-4x+6}{x-2}+\frac{x^2-6x+12}{x-3}\)\(ĐKXĐ:x\ne1;2;3;4\)

\(\Leftrightarrow\frac{\left(x-1\right)^2+1}{x-1}+\frac{\left(x-4\right)^2+4}{x-4}=\frac{\left(x-2\right)^2+2}{x-2}+\frac{\left(x-3\right)^2+3}{x-3}\)

\(\Leftrightarrow\left(\frac{\left(x-1\right)^2}{x-1}+\frac{1}{x-1}\right)+\left(\frac{\left(x-4\right)^2}{x-4}+\frac{4}{x-4}\right)=\left(\frac{\left(x-2\right)^2}{x-2}+\frac{2}{x-2}\right)+\left(\frac{\left(x-3\right)^2}{x-3}+\frac{3}{x-3}\right)\)

\(\Leftrightarrow x-1+\frac{1}{x-1}+x-4+\frac{1}{x-4}=x-2+\frac{1}{x-2}+x-3+\frac{1}{x-3}\)

\(\Leftrightarrow\frac{1}{x-1}+\frac{4}{x-4}=\frac{2}{x-2}+\frac{3}{x-3}\)

\(\Leftrightarrow\frac{x-4+4x-4}{\left(x-1\right)\left(x-4\right)}=\frac{2x-6+3x-6}{\left(x-2\right)\left(x-3\right)}\)

\(\Leftrightarrow\frac{5x-8}{x^2-5x+4}=\frac{5x-12}{x^2-5x+6}\)

\(\Leftrightarrow\left(5x-8\right)\left(x^2-5x+6\right)=\left(5x-12\right)\left(x^2-5x+4\right)\)

Tự giải ra rồi tìm x nhé

6 tháng 7 2018
https://i.imgur.com/XlB7mwa.jpg
6 tháng 7 2018
https://i.imgur.com/E2sWxLH.jpg
2 tháng 7 2018

a)  \(\left(x+6\right)^2-x\left(x+9\right)=0\)

\(\Leftrightarrow\)\(x^2+12x+36-x^2-9x=0\)

\(\Leftrightarrow\)\(3x+36=0\)

\(\Leftrightarrow\)\(x=-12\)

Vậy...

b) \(6x\left(2x+5\right)-\left(3x+4\right)\left(4x-3\right)=9\)

\(\Leftrightarrow\)\(12x^2+30x-12x^2-7x+12=9\)

\(\Leftrightarrow\)\(23x+12=9\)

\(\Leftrightarrow\)\(x=-\frac{3}{23}\)

Vậy

c) \(2x\left(8x+3\right)-\left(4x+1\right)=13\)

\(\Leftrightarrow\)\(16x^2+6x-4x-1=13\)

\(\Leftrightarrow\)\(16x^2+2x-14=0\)

\(\Leftrightarrow\)\(8x^2+x-7=0\)

\(\Leftrightarrow\)\(\left(x+1\right)\left(8x-7\right)=0\)

\(\Leftrightarrow\)\(\orbr{\begin{cases}x=-1\\x=\frac{7}{8}\end{cases}}\)

Vậy

d) \(\left(x-4\right)^2-x\left(x+4\right)=0\)

\(\Leftrightarrow\)\(x^2-8x+16-x^2-4x=0\)

\(\Leftrightarrow\)\(-12x+16=0\)

\(\Leftrightarrow\)\(x=\frac{4}{3}\)

Vậy

e) \(\left(x-2\right)^2-\left(2x+3\right)\left(x-2\right)=0\)

\(\Leftrightarrow\)\(x^2-4x+4-2x^2+x+6=0\)

\(\Leftrightarrow\)\(-x^2-3x+10=0\)

\(\Leftrightarrow\)\(\left(2-x\right)\left(x+5\right)=0\)

\(\Leftrightarrow\)\(\orbr{\begin{cases}x=2\\x=-5\end{cases}}\)

Vậy