А) (7x-1) (2-x) = (x-3) (3-7x)

б) (a-3) (a+4) - (a+2) (a+7) при a=-1/8

в) (m-n+10) (m+n)

А) (7 х-1) (2-х) = (х-3) (3-7 х)

14x-7x^2-2+x-3x+7x^2+9-21x

-9x = - 7

x=7/9

Б) (a-3) (a+4) - (a+2) (a+7) = a^2+4a-3a-12 - (a^2+7a+2a+14) = a^2+a-12-a^2-7a-2a+14=2-8a

Если а=-1/8 то 2-8*-1/8=1

В) (m-n+10) (m+n) = m^2-n^2+10 (m+n)