Verified answer

f(x+7) = 1/(x+7)

f(x+8) = 1/(x+8)

1/(x+7) = 8/(x+8)

x+8 = 8(x+7)

x+8 = 8x + 56

7x = -48

x = -6 целых 6/7

y = f(x), f(x) = 1/x

=> f(x + 7) = 1/(x + 7)

f(x + 8) = 1/(x + 8)

По условию f(x + 7) = 8(x + 8), тогда:

1/(x + 7) = 8/(x + 8), x ≠ -7. x ≠ -8

8(x + 7) = x + 8

8x + 56 = x + 8

8x - x = 8 - 56

7x = -48

x = -48/7 = -6 6/7

Ответ: -6 6/7.