7m(4m-5)-(m-4)(m-9)

28m²-35m-(m²-9m-4m+36)

28m²-35m-m²+13m-36

27m²-22m-36

2

1) (3x+12-2x-6):12=2

x+6=24

x=18

2)

(x-4)(x+2)=(x-5)(x+6)-x

x²+2x-4x-8=x²+6x-5x-30-x

x²-2x-8=x²-30

x²-x²-2x-8+30=0

-2x+22=0

-2x= -22

x=11

3

10ab-5b²-6a+3b ; a=31/5 b=2,4

5b(2a-b)-3(2a-b)

(2a-b)(5b-3)

(2* 31/5 -2,4)(5*2,4-3)=10*9=90

Объяснение: