SOLUTION: Can you please give me the proper equation for (f o g)(3) given f(x) = 11x + 5 and g(x) = x2 + 8x? Also, (g o f)(2), Given f(x) = 2x + 9 and g(x) = x2 + 7x. Please keep in mi

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Can you please give me the proper equation for (f o g)(3) given f(x) = 11x + 5 and g(x) = x2 + 8x? Also, (g o f)(2), Given f(x) = 2x + 9 and g(x) = x2 + 7x. Please keep in mi      Log On


   

Question 4808: Can you please give me the proper equation for (f o g)(3) given f(x) = 11x + 5 and g(x) = x2 + 8x?
Also, (g o f)(2), Given f(x) = 2x + 9 and g(x) = x2 + 7x.
Please keep in mind I have a math learning disability, so the simpler the explanation, the better I'll understand it. I'm 46 and if I don't pass this class, I don't graduate in May. :) Thanks for your help!
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
(f o g)(3) given f%28x%29+=+11x+%2B+5 and g%28x%29+=+x%5E2+%2B+8x
(f o g)(3) means f[ g(3) ], so the first order of business is to find g(3). Go to the g(x) formula and substitute 3 for the x, giving you 3%5E2+%2B+8%2A+3
g(3) = 9 + 24 = 33
Now, find f[ g(3) ] = f[ 33 ] = 11*33 + 5 = 3685



Second problem (g o f)(2), Given f%28x%29+=+2x+%2B+9+and g%28x%29+=+x%5E2+%2B+7x
(g o f)(2) means g[ f(2) ], so you first have to find f(2) using the f(x) formula.
f(2) = 2*2 + 9 = 13
Now you have to find g(13) using the g(x) formula:
(g o f)(2) = g[ f(2) ] = g[ 13 ] = 13%5E2+%2B+7%2A+13 = 169 + 91 = 260

There really isn't a good way to check these without going to twice as much work as solving them to begin with. Such ugly answers! Sorry about that.

R^2 at SCC