Question

Tìm x 

a) 2(x+5)-x²-5x=0

b) 5(x+3)-2x(3+x)=0

Answer 1

\(a,\\ 2\left(x+5\right)-\left(x^2+5x\right)=0\\ 2\left(x+5\right)-x\left(x+5\right)=0\\ \left(2-x\right)\left(x+5\right)=0\\ \left[{}\begin{matrix}2-x=0\\x+5=0\end{matrix}\right.\left[{}\begin{matrix}x=2\\x=-5\end{matrix}\right.\)

\(b,5\left(x+3\right)-2x\left(x+3\right)=0\\ \left(5-2x\right)\left(x+3\right)=0\\ \left[{}\begin{matrix}5-2x=0\\x+3=0\end{matrix}\right.\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-3\end{matrix}\right.\)