1) -6c(4c-d) = -24c² + 6cd
2) $$6mn^3(2m^3-m^2n+3n^4) = 12m^4n^3 - 6m^3n^4 + 18mn^7$$
3) $$(9x+y)(4x-3y) = 36x^2-27xy+4xy-3y^2=36x^2-23xy-3y^2$$
4) $$(x-4)(x^2+2x-3) = x^3+2x^2-3x-4x^2-8x+12=x^3-2x^2-11x+12$$
Ответ:
1) $$-24c^2+6cd$$ 2) $$12m^4n^3 - 6m^3n^4 + 18mn^7$$ 3) $$36x^2-23xy-3y^2$$ 4) $$x^3-2x^2-11x+12$$