Объяснение:
1. 2x²+7xy-5x²-11xy+3y²=-3x²-4xy+3y²
2. -(8c²+3c)+(-7c²-11c+3)-(3c²-4)=-8c²-3c-7c²-11c+3-3c²+4=-18c²-14c+7
3. x(x³+x²+x)-x²(x³+x²+x)=x⁴+x³+x²-x⁵-x⁴-x³=-x⁵+x²
4. -5x⁴(2x-x³)+10x⁵=-10x⁵+5x⁷+10x⁵=5x⁷
5. (x³+2y)(x²-2y)-(x²+2y)(x³-2y)=x⁵-2x³y+2x²y-4y²-x⁵+2x²y-2x³y+4y²=-4x³y+4x²y
