Question

\[x=\sqrt{42-x}\]

Answer 1

Square both sides we have
\(x^2=42-x\)
\(x^2+x-42=0\)
\((x+7)(x-6)=0\)
\(x=-7\) or \(x=6\)
But if we plu gin \(x=-7\) to the original equation it doesn't work!
So \(x=6\)