9^x+2*3^x=15 помогите!!!

Question

9^x+2*3^x=15 помогите!!!

Answer 1

9^x + 2•3^x = 15
3^x = a ( a > 0 )
a^2 + 2a - 15 = 0
D = 4 + 60 = 64 = 8^2
a1 = ( - 2 + 8 ) : 2 = 3
a2 = ( - 2 - 8 ) : 2 = - 5 ( < 0 )
3^x = 3
X = 1

Comments

спасибо огромное !!!