(х-4)(х+5)-(х-7)(х+7)=-7

x(x + 5) - 4(x + 5) - (x - 7)(x + 7) = - 7

x ^ 2 + 5x - 4(x + 5) - (x - 7)(x + 7) = - 7

x ^ 2 + 1x - 20 - (x - 7)(x + 7) = - 7

x ^ 2 + x - 20 - (x(x + 7) - 7(x + 7)) = - 7

x ^ 2 + x - 20 - (x ^ 2 + 7x - 7(x + 7)) = - 7

x ^ 2 + x - 20 - (x ^ 2 + 7x - 7x - 49) = - 7

x ^ 2 + x - 20 - (x ^ 2 - 49) = - 7

x ^ 2 + x - 20 - x ^ 2 + 49 = - 7

x ^ 2 + x + 29 - x ^ 2 = - 7

x + 29 = - 7

x + 29 - 29 = - 7 - 29

x = - 36

Відповідь: - 36