Решение:
A) $$(x-8)(x+5) = x^2 + 5x - 8x - 40 = x^2 - 3x - 40$$
Б) $$(3b-2)(4b-2) = 12b^2 - 6b - 8b + 4 = 12b^2 - 14b + 4$$
В) $$(6a+x)(2a-3x) = 12a^2 - 18ax + 2ax - 3x^2 = 12a^2 - 16ax - 3x^2$$
Г) $$(c+1)(c^2+3c+2) = c^3 + 3c^2 + 2c + c^2 + 3c + 2 = c^3 + 4c^2 + 5c + 2$$