# Thread: how to solve this exponential equation?

1. ## how to solve this exponential equation?

whats solution to (3)^2x-36(3)^x+243=0

2. ## Re: how to solve this exponential equation?

$\displaystyle (3^x)^2-36(3^x)+243=0$

Substitute $\displaystyle y=3^x$ if you like. Factorise.

3. ## Re: how to solve this exponential equation?

then you just use quadratic formula?

4. ## Re: how to solve this exponential equation?

That will certainly work.

5. ## Re: how to solve this exponential equation?

your solution set is 9, -27, but when i try testing them with original equation im not getting right answer, is there something im missing

6. ## Re: how to solve this exponential equation?

Originally Posted by kukid13
your solution set is 9, -27, but when i try testing them with original equation im not getting right answer, is there something im missing
you should have found 9 and +27 for your quadratic solutions ..

7. ## Re: how to solve this exponential equation?

but when i try to plug those back into equation im coming up with funky answers? what am i missing

8. ## Re: how to solve this exponential equation?

Originally Posted by kukid13
but when i try to plug those back into equation im coming up with funky answers? what am i missing
$\displaystyle 3^x = 9$

$\displaystyle x = 2$

you do the other solution ...