Решить систему
(8/7)^x×(7/8)^-y=64/49
(21)^-8=21^xy
5^x>5^y

(8/7)^x×(7/8)^-y=64/49

(21)^-8=21^xy

5^x>5^y

(8/7)^x×(8/7)^y=(8/7)^2

-8=xy

x>y

x+y=2

xy = -8

x>y

x = 2 - y

y(2 - y) = -8

2y - y^2 = - 8

y^2 - 2y - 8 = 0

D = 4 + 32 = 36

y12 = (2 +- 6)/2 = -2   4

1. y1 = -2

x1 = 2 - (-2) = 4

4 > -2 да

2. y2 = 4

x2 = 2 - 4 = -2

-2 < 4 нет

ответ (4, -2)