Question

Rút gọn biểu thức : (x - 5)( 2x + 3) - 2x( x - 3 ) + x - 7

Answer 1

\(\left(x-5\right)\left(2x+3\right)-2x\left(x-3\right)+x-7\)

\(=\left(2x^2+3x-10x-15\right)-\left(2x^2-6x\right)+x-7\)

\(=2x^2-7x-15-2x^2+6x+x-7\)

\(=-22\)

Answer 2

\(\left(x-5\right)\left(2x+3\right)-2x\left(x-3\right)+x-7\)

\(=2x^2+3x-10x-15-\left(2x^2-6\right)+x-7\)

\(=2x^2+3x-10x-15-2x^2+6x+x-7\)

\(=\left(2x^2-2x^2\right)+\left(3x-10x+6x+x\right)-15-7\)

\(=-22\)

Answer 3

\(\hept{\begin{cases}\frac{x^2}{2}-\frac{1}{2}=y\left(1-x-y\right)\\x\left(3x+2y-2\right)=y^2-y+5\end{cases}}\)