Question

Rút gọn biểu thức

a, (x-2).(x+2)+(x-3).(x+3)-2x^2

b, (x+5).(x-5)+(x-7).(x+7)-2x^2

Answer 1

a) ( x - 2 )(x + 2 ) + ( x - 3 )( x + 3 ) - 2x²

= x² - 4 + x² - 9 - 2x²

= - 4 - 9 = - 13

b ) ( x - 5 )(x + 5 ) + ( x - 7 )( x + 7 ) - 2x²

= x² - 25 + x² - 49 - 2x²

= - 25 - 49 = - 84

Answer 2

a) (x - 2).(x + 2) + (x - 3).(x + 3) - 2x²

= x² + 2x - 2x - 4 + x² + 3x - 3x - 9 - 2x²

= - 4 - 9

= -13.

b) (x + 5).(x - 5) + (x - 7).(x + 7) - 2x²

= x² - 5x + 5x - 25 + x² + 7x - 7x - 49 - 2x²

= - 25 - 49

= -74.