Question 936159
Use the substitution y=3^x to find the values of x which satisfy the equation 
3^(2x+2)-10*3^(x) +1=0

I tried: 3^(2)*3^(x)  + 3^(2)  -10*3^(x) + 1 =0
It's 3^2*3^(2x) -10*3^x + 1 = 0
--> 9y^2 - 10y + 1 = 0
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You had the right idea, but having 2 answers should make you expect a quadratic.
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Substituted in y:   9y + 9 - 10y + 1 = 0
which became:  -y=-9 then y=9
so 3^x = 9 therefore x is 2 or so I thought. 
The textbook answer given is -2 and 0.