Question

tìm x 

(x+5)*(2x+1)=0

x(x+2)-3*(x+2)=0

2*(x+5)-x^2-5x=0

Answer 1

`a, (x+5)(2x+1) = 0`

`<=>` \(\left[{}\begin{matrix}x+5=0\\2x+1=0\end{matrix}\right.\)

`<=>` \(\left[{}\begin{matrix}x=-5\\x=-\dfrac{1}{2}\end{matrix}\right.\)

`b, (x-3)(x+2) = 0`

`<=>` \(\left[{}\begin{matrix}x-3=0\\x+2=0\end{matrix}\right.\)

`<=>` \(\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

`c, 2(x+5) - x(x+5) = 0`

`<=> (2-x)(x+5) = 0`

`<=>`\(\left[{}\begin{matrix}2-x=0\\x+5=0\end{matrix}\right.\)

`<=>` \(\left[{}\begin{matrix}x=2\\x=-5\end{matrix}\right.\)

Answer 2

\((x+5)(2x+1)=0\) 

\(<=>[(x+5)=0<=>[x=-5\) 

\(<=>(2x+1)=0<=>[x=\dfrac{-1}{2}\) 

\(x(x+2)-3(x+2)=0\) 

\(<=>(x+2)(x-3)=0\) 

\(<=>[(x+2)=0<=>[x=-2\) 

\(<=>[(x-3)=0<=>[x=3\) 

\(2(x+5)-x^2-5x)=0\) 

\(<=>2(x+5)-x(x+5)=0\) 

\(<=>(x+5)(2-x)=0\) 

\(<=>[(x+5)=0<=>[x=-5\) 

\(<=>[(2-x)=0<=>[x=2\)