Question

Решите пожалуйста.
49^x-5*7^x-14=0

Answer 1

49^х - 5•7^х - 14 = 0
7^х = а ; a > 0
а^2 - 5а - 14 = 0
D = 25 + 56 = 81
a1 = ( 5 + 9 ) : 2 = 7
a2 = ( 5 - 9 ) : 2 = - 2
7^x = 7
X = 1