Question

Упростите: а) (x+4)(x-5)+20; б) (3x-4y)(3x+4y); в) -4b(b-2)+(b-5)^2

Answer 1

Ответ:

х 2-5х+4х-20+20=х2-х

9х 2+12ху-12ух-16у =9х 2-16у

Answer 2

а) (x+4)(x-5)+20: (x+4)(x-5) = x(x-5) + 4(x-5) = x^2 - 5x + 4x - 20 = x^2 - x - 20 (x+4)(x-5) + 20 = x^2 - x - 20 + 20 = x^2 - x

б) (3x-4y)(3x+4y): (3x-4y)(3x+4y) = (3x)^2 - (4y)^2 = 9x^2 - 16y^2

в) -4b(b-2) + (b-5)^2: -4b(b-2) = -4b^2 + 8b (b-5)^2 = b^2 - 10b + 25

-4b(b-2) + (b-5)^2 = -4b^2 + 8b + b^2 - 10b + 25 = -3b^2 - 2b + 25