Ответ:
1. а) (3a-7b)-(4a+8b) = 3a-7b-4a-8b = -a-15b
б) -(5m-7n)+(2n+12m) = -5m+7n+2n+12m = 7m+9n
в) 3x(1-4x)-5x(6x+7) = 3x-12x²-30x²-35x = -32x-42x²
г) 5c(2c+a)+(3c-2a)(5a-2c) = 10a²+5ac+15ac-6c²-10a²+4ac = 4c²+24ac-10a²
д) (5y-3)²-(2-5y)² = 25y²-30y+9-(4-20y+25y²) = 25y²-30y+9-4+20y-25y² = -10y+5