Question

Xác định giá trị của x thỏa mãn:\(\left(x-1\right)\left(x+2\right)-x^2=5\)

Answer 1

\(\left(x-1\right)\left(x+2\right)-x^2=5\)

\(\Leftrightarrow x^2+2x-x-2-x^2=5\)

\(\Leftrightarrow x-2=5\)

\(\Leftrightarrow x=7\)

Answer 2

\(\left(x-1\right)\left(x+2\right)-x^2=5\)

\(\Leftrightarrow\left(x-1\right)\left(x+2\right)-x^2-5=0\)

\(\Leftrightarrow\left(x^2-x^2\right)+\left(2x-x\right)-\left(2+5\right)\)

\(\Leftrightarrow x-7=0\)

\(\Leftrightarrow x=0+7\)

\(\Leftrightarrow x=7\)

Answer 3

\(\left(x-1\right)\left(x+2\right)-x^2=5\)

\(x^2+x-2-x^2=5\)

\(x-2-5=0\)

\(x-7=0\)

\(x=7\)

           Vậy \(x=7\)