# Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3

• Mar 10th 2012, 12:44 PM
Lotte1990
Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3
Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3

Does anyone know how to find g?

I tried the following:

sqrt(x) results in x + 3 which is wrong...
sqrt(x) + 2 results in x + 4sqrt(x) + 7 which is wrong...
etc...

• Mar 10th 2012, 12:48 PM
Lotte1990
Re: Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3
Nevermind, sqrt(x + 2) is the right answer. I finally found it!
• Mar 10th 2012, 12:54 PM
Plato
Re: Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3
Quote:

Originally Posted by Lotte1990
Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3

Does anyone know how to find g?

Can you solve \$\displaystyle {y^2} + 3 = 5 + x\$ for \$\displaystyle y~?\$
• Mar 12th 2012, 12:18 PM
DrSteve
Re: Find g for f(g(x)) = 5 + x when f(x) = x^2 + 3
Quote:

Originally Posted by Lotte1990
Nevermind, sqrt(x + 2) is the right answer. I finally found it!

Looks like g can be the negative of this as well.