Question

Tìm số nguyên x biết: (x+1)^2 - 15 = 85

 

Answer 1

 `(x+1)^2 - 15 = 85`

`=>(x+1)^2=85+15`

`=>(x+1)^2=100`

`=>(x+1)^2=+-10^2`

\(\Rightarrow\left[{}\begin{matrix}x+1=10\\x+1=-10\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=9\\x=-11\end{matrix}\right.\)

Answer 2

Answer 3

\(\left(x+1\right)^2-15=85\\ \Rightarrow x^2+2x+1-15=85\\ \Rightarrow x^2+2x-99=0\\ \Rightarrow\left\{{}\begin{matrix}x-9=0\Rightarrow x=9\\x+11=0\Rightarrow x=-11\end{matrix}\right.\)