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1)=>3(x-5)(2x+9)+3(x-5)=0=>(x-5)(6x+30)
=>x-5=0=>x=5
6x+30=0=>x=-5
2)=>x^2-16=0=>x=+-4
12-4x=0=>x=3
3)=>9-x^2=0=>x=+-3
4x-8=0=>x=2
4)=>8-x^3=0=>x=3
5^x-125=0=>x=2
5)=>2^x.2^x=8=>2^2x=8=>2x=3=>x=1,5
Bài này giống tìm nghiệm quá :
1) \(5\left(x-7\right)=0\)
\(\left(x-7\right)=0\div5\)
\(\left(x-7\right)=0\)
\(x=0+7\)
\(x=7\)
2) \(25\left(x-4\right)=0\)
\(\left(x-4\right)=0\div25\)
\(\left(x-4\right)=0\)
\(x=0+4\)
\(x=4\)
3) \(34\left(2x-6\right)=0\)
\(\left(2x-6\right)=0\div34\)
\(\left(2x-6\right)=0\)
\(2x=0+6\)
\(2x=6\)
\(x=6\div2\)
\(x=3\)
4) \(2007\left(3x-12\right)=0\)
\(\left(3x-12\right)=0\div2007\)
\(\left(3x-12\right)=0\)
\(3x=0+12\)
\(3x=12\)
\(x=12\div3\)
\(x=4\)
5) \(47\left(5x-15\right)=0\)
\(\left(5x-15\right)=0\div47\)
\(\left(5x-15\right)=0\)
\(5x=0+15\)
\(5x=15\)
\(x=15\div5\)
\(x=3\)
6) \(13\left(4x-24\right)=0\)
\(\left(4x-24\right)=0\div13\)
\(\left(4x-24\right)=0\)
\(4x=0+24\)
\(4x=24\)
\(x=24\div4\)
\(x=6\)
a: -5x-16=x+40
=>-6x=56
hay x=-28/3
b: \(4x-10=15-x\)
=>5x=25
hay x=5
c: \(-12\left(x-5\right)+7\left(3-x\right)=5\)
=>-12x+60+21-7x=5
=>-19x+71=5
=>-19x=-76
hay x=4
d: \(\left(x-2\right)\left(x+15\right)=0\)
=>x-2=0 hoặc x+15=0
=>x=2 hoặc x=-15
\(\left(4x+12\right)\left(x+5\right)=0\\ \Rightarrow\left[{}\begin{matrix}4x+12=0\\x+5=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}4x=-12\\x=-5\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=-3\\x=-5\end{matrix}\right.\)
Vậy: \(x\in\left\{-3;-5\right\}\)
(4x+12)(x+5)=0
=>4(x+3)(x+5)=0
=>(x+3)(x+5)=0
=>\(\left[{}\begin{matrix}x+3=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-5\end{matrix}\right.\)