Question

`25(x^2 -1)-75=9900`

Answer 1

\(25\left(x^2-1\right)-75=9900\)

\(\Rightarrow25\left(x^2-1\right)=9975\)

\(\Rightarrow x^2-1=399\)

\(\Rightarrow x^2=400=\left(\pm20\right)^2\)

\(\Rightarrow\left[{}\begin{matrix}x=20\\x=-20\end{matrix}\right.\)

Answer 2

\(25\left(x^2-1\right)=9975\\ \left(x^2-1\right)=399\\ x^2=400\\ =>\left[{}\begin{matrix}x=20\\x=-20\end{matrix}\right.\)