Tìm số nguyên x, biết: a) 28 + x = -59 b) (x−4)(x^2 −25)=0 c) |x+2|=17

* Hướng dẫn giải

$\begin{array}{l}a)28+x=-59\\ x=-59-28\\ x=-87\end{array}$

$\begin{array}{l}b)\left(x-4\right)\left(x^2-25\right)=0\\ \iff \left[\begin{array}{l}x-4=0\\ x^2-25=0\end{array}\right.\iff \left[\begin{array}{l}x=4\\ x^2=25\end{array}\right.\iff \left[\begin{array}{l}x=4\\ x=\pm 5\end{array}\right.\end{array}$

$\begin{array}{l}\left|x+2\right|=17\\ \Rightarrow \left[\begin{array}{l}x+2=17\\ x+2=-17\end{array}\right.\Rightarrow \left[\begin{array}{l}x=15\\ x=-19\end{array}\right.\end{array}$

$\begin{array}{l}d)-19+4(2-x)=25-x\\ -19+8-4x=25-x\\ 4x-x=-19+8-25\\ 3x=-36=>x=-12\end{array}$