Объяснение:

1) 5а(а⁵-6а³+4) = 5а⁶-30а⁴+20а

2) (х+6)(3х-2) = 3х²-2х+18х-12 = 3х²+16х-12

3) (6m+5n)(7m-3n) = 42m²-18mn+35mn-15n² = 42m²+17mn-15n²

4) (x²+5)(x+x²-6) = x³+x⁴-6x²+5x+5x²-30 = x³+x⁴-x²+5x-30