$4 b c-\left(3 b^2 c-5 b c^2\right)-\left[2 b^2 c-\left(7 b c-3 b c^2\right)+8 b c-5 b^2 c\right]-2 b c^2$
$4 b c-\left(3 b^2 c-5 b c^2\right)-\left[2 b^2 c-\left(7 b c-3 b c^2\right)+8 b c-5 b^2 c\right]-2 b c^2$
436)
$4bc-(3b^2c-5bc^2)-[2b^2c-(7bc-3bc^2)+8bc-5b^2c]-2bc^2$ =
= $4bc-3b^2c+5bc^2-[2b^2c-7bc+3bc^2+8bc-5b^2c]-2bc^2$ =
= $4bc-3b^2c+5bc^2-[-3b^2c+bc+3bc^2]-2bc^2$ =
= $4bc-3b^2c+5bc^2+3b^2c-bc-3bc^2-2bc^2$ =
= $3bc$