(7b-8)(8b+7)-8b(7b+8) При b=2,6

Question

(7b-8)(8b+7)-8b(7b+8)
При b=2,6

Answer 1

=56b²(вычеркиваем)+49b-64b-56-56b²(вычеркиваем)-64b=-79b-56=-79x2,6 - 56=-76,54

Answer 2

(7b-8)(8b+7)-8b(7b+8)=56b+49b-64b-56-56b-64b=-79b-56
b=5,6
-79×5,6-56=-496,4