Question

а) (2b – 3) (5b + 7) + 21, якщо b = -2

Answer 1

10b 2 14b-15b 10b2 -b otvet :10b2-b

Answer 2

$(2b-3)(5b+7) + 21 = 2b \cdot5b+2b \cdot7-3 \cdot5b-3 \cdot7 =\\\\= 10b^2+14b-15b-21+21 = \\\\ =10b^2-b = 10 \cdot(-2)^2-(-2) = 10 \cdot 2^2+2 = 42$