Question

rút gọn biểu thức sau

a) ( x - 3 ) ( x + 7 ) - ( x + 5 ) ( x - 1 )

Answer 1

a) ( x - 3 ) ( x + 7 ) - ( x + 5 ) ( x - 1 )

= ( x² +7x - 3x - 21 ) - ( x² -x + 5x - 5 )

= x² + 4x -21 - x² - 4x +5

= -16

Answer 2

a: Ta có: \(\left(x-3\right)\left(x+7\right)-\left(x+5\right)\left(x-1\right)\)

\(=x^2+4x-21-x^2-4x+5\)

=-16