Ответ:
1) (c-7)(c+2) = c*c+2c-7c-7*2 = c²+2c-7c-7*2 = c²-5c-14
2) (5c+2)(1-2c) = 5c-5c*2c+2-2*2c = 5c-10c²+2-4c = c-10c²+2 = -10c²+c+2
3) (3c-2d)(d-c) = 3cd-3c*c-2d*d-2d(-c) = 3cd-3c²-2d²+2cd = 5c-3c²-2d²
4) (5c+8)(2-9c) = 5c*2-5c*9c+8*2-8*9c = 10c-45c²+16-72c = -62-45c²+16 =
= -45c²-62c+16
5) (a+b)(3a-b+2) = a(3a-b+2)+b(3a-b+2) = 3a²-ab+2a+3ab-b²+2b =
=3a²+2ab+2a-b²+2b
6) (x²+1)(4-x²) = 4x²-x²*x²+4-x² = 4x²-x^4+4 = -x^4+3x²+4
7) (5-x)(5+x) = 5²-x² = 25-x²
8) (5-x)(5-x) = (5-x)²