Question

Выполните умножение
(0,2d-5c)(5c+0,2d)
(9-k)(9+k)

Answer 1

Объяснение:

$(0.2d - 5c)(5c + 0.2d) =\left(0.2d\right)^{2}-\left(5c\right)^{2} =0.2^{2}d^{2}-\left(5c\right)^{2} =0.04d^{2}-\left(5c\right)^{2} =0.04d^{2}-5^{2}c^{2} =0.04d^{2}-25c^{2}$

$(9 - k)(9 + k) = 9 {}^{2} - k {}^{2} = 81 - k {}^{2}$