Question

Tìm x biết : \(\sqrt{7-x}=x+1\)

Answer 1

\(\Leftrightarrow7-x=\)\(\left(x+1\right)^2\)

\(\Leftrightarrow\)7-x=x²+2x+1

\(\Leftrightarrow\)x²+3x-6=0

\(\Leftrightarrow\)(\(x-\frac{-3+\sqrt{33}}{2}\))\(\times\)(\(x-\frac{-3-\sqrt{33}}{2}\))=0

\(\Leftrightarrow\)x=\(\frac{-3+\sqrt{33}}{2}\)hoặc  x=\(\frac{-3-\sqrt{33}}{2}\)