Question

показательное уравнение 9^х-8*3^х=9

Answer 1

9 ^ x - 8 • 3 ^ x = 9
3 ^2x - 8•3^x = 9
3^x = a ; a > 0
a^2 - 8a - 9 = 0
D = 64 + 36 = 100 ; VD = 10
a1 = ( 8 + 10 ) : 2 = 9
a2 = ( 8 - 10 ) : 2 = - 1
3^x = 9
3^x = 3^2
x = 2
Ответ х = 2