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\(a,12x=4x-30\Leftrightarrow8x=-30\Leftrightarrow x=-\dfrac{15}{4}\)
\(b,2x-5=x-1\Leftrightarrow2x-x=-1+5\Leftrightarrow x=4\)
\(c,2-5x=5x-10\Leftrightarrow-10x=-12\Leftrightarrow x=\dfrac{6}{5}\)
\(d,9x-6=1x-5\Leftrightarrow8x=1\Leftrightarrow x=\dfrac{1}{8}\)
\(e,2x-5=2x-1\Leftrightarrow2x-2x=-1+5\Leftrightarrow0x=4\) (Vô lí)\(\Rightarrow x\in\varnothing\)
a) 6x(5x + 3) + 3x(1 – 10x) = 7
⇒ 30x2+18x+3x-30x2=7
⇒21x=7
⇒x=\(\dfrac{7}{21}\)
⇒x= \(\dfrac{1}{3}\)
b) (3x – 3)(5 – 21x) + (7x + 4)(9x – 5) = 44
⇒15x-63x2-15+63x + 63x2-35x+36x-20=44
⇒79x-35=44
⇒79x=44+35
⇒79x=79
⇒x=1
\(\left|2x-\frac{1}{2}\right|+1=3x\)
\(\Leftrightarrow\left|2x-\frac{1}{2}\right|=3x-1\)
\(\Leftrightarrow\orbr{\begin{cases}2x-\frac{1}{2}=3x-1\\2x-\frac{1}{2}=1-3x\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}2x-3x=-1+\frac{1}{2}\\2x+3x=1+\frac{1}{2}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}-x=-\frac{1}{2}\\5x=\frac{3}{2}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{3}{10}\end{cases}}\)
1. Rút gọn biểu thức :
\(M=4.\left(2-3x\right)-\left|2x-3\right|\) (*)
- Xét 2 TH :
+ Trường hợp 1 : \(\left|2x-3\right|=\left(2x-3\right)\) thì (*) trở thành :
\(M=4.\left(2-3x\right)-\left(2x-3\right)\)
\(\Rightarrow M=8-12x-2x+3\)
\(\Rightarrow M=-14x+11\)
+ Trường hợp 2 : \(\left|2x-3\right|=\left(3-2x\right)\) thì (*) trở thành :
\(M=4.\left(2-3x\right)-\left(3-2x\right)\)
\(\Rightarrow M=8-12x-3+2x\)
\(\Rightarrow M=-10x+5\)
a) \(A\left(x\right)=-2x+3x-4x^3+\frac{3}{5}-5x^4\)
\(\Rightarrow A\left(x\right)=-5x^4-4x^3-2x+3x+\frac{3}{5}\)
\(\Rightarrow A\left(x\right)=-5x^4-4x^3+x+\frac{3}{5}\)
\(B\left(x\right)=3x^4+\frac{1}{5}-7x^2+5x^3-9x\)
\(\Rightarrow B\left(x\right)=3x^4+5x^3-7x^2-9x+\frac{1}{5}\)
b) \(A\left(x\right)+B\left(x\right)\)
\(=-5x^4-4x^3+x+\frac{3}{5}+3x^4+5x^3-7x^2-9x+\frac{1}{5}\)
\(=\left(-5x^4+3x^4\right)+\left(-4x^3+5x^3\right)-7x^2+\left(x-9x\right)+\left(\frac{3}{5}+\frac{1}{5}\right)\)
\(=-2x^4+x^3-7x^2-8x+\frac{4}{5}\)
\(A\left(x\right)-B\left(x\right)\)
\(=\left(-5x^4-4x^3+x+\frac{3}{5}\right)-\left(3x^4+5x^3-7x^2-9x+\frac{1}{5}\right)\)
\(=\left(-5x^4-3x^4\right)+\left(-4x^3-5x^3\right)+7x^2+\left(x+9x\right)+\left(\frac{3}{5}-\frac{1}{5}\right)\)
\(=-8x^4-9x^3+7x^2+10x+\frac{2}{5}\)
Chúc bạn học tốt !
I don't now
or no I don't
..................
sorry
a)\(x+12x+x+12x+1=0,5x+2x+30,5x+2x+3\)
\(\Leftrightarrow26x+1=35x+3\)
\(\Leftrightarrow26x+1-\left(35x+3\right)=0\)
\(\Leftrightarrow26x+1-35x-3=0\)
\(\Leftrightarrow-9x+\left(-2\right)=0\)
\(\Leftrightarrow-9x=2\)
\(\Leftrightarrow x=-\frac{2}{9}\)
\(A+B=\left(3x^4-\frac{3}{4}x^3+2x^3-1\right)+\left(8x^4+\frac{1}{5}x^3-9x+\frac{2}{5}\right)\)
\(=3x^4+\frac{5}{4}x^3-1+8x^4+\frac{1}{5}x^3-9x+\frac{2}{5}\)
\(=11x^4+\frac{29}{20}x^3-9x-\frac{3}{5}\)
Các phần còn lại tương tự nha bạn
Bài 1:
a) -6x + 3(7 + 2x)
= -6x + 21 + 6x
= (-6x + 6x) + 21
= 21
b) 15y - 5(6x + 3y)
= 15y - 30 - 15y
= (15y - 15y) - 30
= -30
c) x(2x + 1) - x2(x + 2) + (x3 - x + 3)
= 2x2 + x - x3 - 2x2 + x3 - x + 3
= (2x2 - 2x2) + (x - x) + (-x3 + x3) + 3
= 3
d) x(5x - 4)3x2(x - 1) ??? :V
Bài 2:
a) 3x + 2(5 - x) = 0
<=> 3x + 10 - 2x = 0
<=> x + 10 = 0
<=> x = -10
=> x = -10
b) 3x2 - 3x(-2 + x) = 36
<=> 3x2 + 2x - 3x2 = 36
<=> 6x = 36
<=> x = 6
=> x = 5
c) 5x(12x + 7) - 3x(20x - 5) = -100
<=> 60x2 + 35x - 60x2 + 15x = -100
<=> 50x = -100
<=> x = -2
=> x = -2