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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
a: 2x-1=0
nên 2x=1
hay x=1/2
b: 4x2-16=0
=>(x-2)(x+2)=0
=>x=2 hoặc x=-2
c: x2-2x=0
=>x(x-2)=0
=>x=0 hoặc x=2
a) \(\left(2x-3\right)\left(2x+3\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}2x-3=0\\2x+3=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x=3\\2x=-3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)
b) \(\left(x-4\right)\left(x-1\right)\left(x-2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-4=0\\x-1=0\\x-2=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=4\\x=1\\x=2\end{matrix}\right.\)
c) \(2x\left(3x-1\right)-3x\left(5+2x\right)=0\)
\(\Rightarrow x\left[2\left(3x-1\right)-3\left(5+2x\right)\right]=0\)
\(\Rightarrow x\left(6x-2-15-6x\right)\)
\(\Rightarrow-16x=0\)
\(\Rightarrow x=0\)
d) \(\left(3x-2\right)\left(3x+2\right)-4\left(x-1\right)=0\)
\(\Rightarrow9x^2-4-4x+4=0\)
\(\Rightarrow9x^2-4x=0\)
\(\Rightarrow x\left(9x-4\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\9x-4=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{4}{9}\end{matrix}\right.\)
\(a,\left(2x-3\right)\left(2x+3\right)=0\Leftrightarrow\left[{}\begin{matrix}2x-3=0\\2x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\\ b,\left(x-4\right)\left(x-1\right)\left(x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x-4=0\\x-1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=1\\x=2\end{matrix}\right.\)
Lời giải:
a. $7-4(x+1)=3x-5$
$7-4x-4=3x-5$
$3-4x=3x-5$
$3+5=3x+4x$
$8=7x$
$x=\frac{8}{7}$
------------------------
c.
$\frac{5x+8}{3}=\frac{4-2x}{4}$
$\Rightarrow 4(5x+8)=3(4-2x)$
$\Rightarrow 20x+32=12-6x$
$\Rightarrow 20x+6x=12-32$
$\Rightarrow 26x=-20$
$\Rightarrow x=\frac{-20}{26}=\frac{-10}{13}$
-------------------
d.
$(9x-1)^2=5=(\sqrt{5})^2=(-\sqrt{5})^2$
$\Rightarrow 9x-1=\sqrt{5}$ hoặc $9x-1=-\sqrt{5}$
$\Rightarrow x=\frac{\sqrt{5}+1}{9}$ hoặc $x=\frac{1-\sqrt{5}}{9}$
\(a,\Rightarrow\left[{}\begin{matrix}x-\dfrac{2}{3}=\dfrac{5}{4}\\\dfrac{2}{3}-x=\dfrac{5}{4}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{23}{12}\\x=-\dfrac{7}{12}\end{matrix}\right.\\ b,\Rightarrow0,1x\cdot1,35=0,2\cdot1,25=0,25\\ \Rightarrow0,135x=0,25\Rightarrow x=\dfrac{50}{27}\\ c,ĐK:x\ge0\\ PT\Leftrightarrow-2\sqrt{x}=-6\Leftrightarrow x=9\left(tm\right)\\ d,\Leftrightarrow3^{x+2}\cdot2^{x-1}=\left(3^2\cdot2^2\right)^3=3^6\cdot2^6\\ \Leftrightarrow\left\{{}\begin{matrix}x+2=6\\x-1=6\end{matrix}\right.\Leftrightarrow x\in\varnothing\)
a) 2x+10=0->2x=-10->x=-5
b) 4(x-1)+3x-5=0->4x-4+3x-5=0
=7x-9=0->7x=-9->x=-1.28571428571
c)-1 1/3x^2+x=0
=-3x^2/-3x^2+x=0
=1+x=0
x=-1
c: =>-4/3x^2+x=0
=>x(-4/3x+1)=0
=>x=0 hoặc x=3/4
a: 2x+10=0
=>2x=-10
=>x=-5
b: =>4x-4+3x-5=0
=>7x-9=0
=>x=9/7
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