Question

(2x-1)(x+7)=x² -49

Answer 1

\(\left(2x-1\right)\left(x+7\right)=x^2-49\)

\(\Leftrightarrow\left(2x-1\right)\left(x+7\right)=\left(x-7\right)\left(x+7\right)\)

\(\Leftrightarrow\left(x+7\right)\left(x+6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-7\\x=-6\end{matrix}\right.\)

Answer 2

(2x-1)(x+7)=\(x^2\) -49

=> (2x-1)(x+7)=(x-7)(x+7)

=> (2x-1)(x+7)-(x-7)(x+7)=0

=>(2x-1-x+7)(x+7)=0

=> x+6=0 hoặc x+7=0

=> x=-6 hoặc x=-7