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 Thread Tools Display Modes 05-19-2015 #1 Dragonballful23    Join Date: Dec 2011 Posts: 386 Hard!!!! Determine what x equals. 9^(x+2)=3^x __________________ Finally finished all my tests!!! I am ekko main now ^_^ (ign: supersaiyan2363) It's not how much time you have, it's how you use it. -Ekko  05-20-2015 #2 eliseo   Join Date: May 2015 Posts: 5 It's infinity  05-22-2015   #3
Dragonballful23    Join Date: Dec 2011
Posts: 386 Quote:
 Originally Posted by eliseo It's infinity
Here is how you solve. since 9^(x+2)=3^x, you can say 3^(2x+4)=3^x

Now, just like when you factor quadratic equations, take out the 3.
3x+4=x
2x=-4
x=-2!
__________________
Finally finished all my tests!!!

I am ekko main now ^_^

(ign: supersaiyan2363)

It's not how much time you have, it's how you use it.
-Ekko  06-09-2015 #4 coolbro   Join Date: Feb 2015 Posts: 1 Now, just like when you factor quadratic equations, take out the 3. 3x+4=x 2x=-4 x=-2!  06-09-2015   #5
MAS1   Join Date: Dec 2008
Posts: 249 Quote:
 Originally Posted by Dragonballful23 Here is how you solve. since 9^(x+2)=3^x, you can say 3^(2x+4)=3^x Now, just like when you factor quadratic equations, take out the 3. 3x+4=x 2x=-4 x=-2!
You made a small mistake.
9^(x+2) = 3^x
(3^2)^(x+2) = 3^x
3^(2(x+2)) = 3^x
3^(2x+4) = 3^x
Since the base numbers are the same (3) then for the equation to be equal the exponents must be equal.
2x+4 = x
2x - x + 4 = x - x
x + 4 = 0
x + 4 - 4 = 0 - 4
x = -4
Let's check our answer.
9^(-4 + 2) = 3^(-4)
9^(-2) = 3^(-4)
1/(9^2) = 1/(3^4)
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