упростите выражение:

1) 2c (5c-3) - (c-2) (c-4)

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

3) (a-4) (a+6) + (a-10) (a-2)

4) (x+1) (x+7) - (x+2) (x+3)

5) (y-3) (5-y) - (4-y) (y+6)

1) 2c (5c-3) - (c-2) (c-4) = 10c^2-6c-c^2+6c-8=9c^2-8

2) (3a+b) (a-2b) + (2a+b) (a-5b) = 3a^2-5ab-2b^2+2a^2-9ab-5b^2 = 5a^2-14ab-7b^2

3) (a-4) (a+6) + (a-10) (a-2) = a^2+2a-24+a^2-12a+20=2a^2-10a-4

4) (x+1) (x+7) - (x+2) (x+3) = x^2+8x+7-x^2-5x-6 = 3x+1

5) (y-3) (5-y) - (4-y) (y+6) = - y^2+8y-15+y^2+2y-24=10y-39