1.
а)5ху×(-3х²)×2у³=-15x³y×2y³=-30x³y⁴
б)-3mn²×5mp²×0,4np=-15m²n²p²×0,4np=-6m²n³p³
2.
f(x)=3x³-4x²+2x-5; g(x)=-3x³+x²-x+8
1)f(x)+g(x)=3x³-4x²+2x-5-3x³+x²-x+8=-3x²+x+3
2) f(x)-g(x)=3x³-4x²+2x-5+3x³-x²+x-8=6x³-5x²+3x-13
3.
1)5ab²×(4a+3b)-3a²b²×(5+7b)=20ab²+15ab³-15a²b²-21a²b³
2)a×(b-3)-3b(a-4)=ab-3a-3ab-12b=-3a-2ab-12b