Solving Composite Functions with Simple Examples

[Peter G.]

I was doing some exercises on composite functions and I got all of the questions right but I can't figure this one out!

gf (1) where g = x² and f = 2x + 1

So, (2x + 1)²

Now I don't know if I sub 1 into x already or if I expand, but, anyhow, I don't know how the book got 1 as an answer!

Thanks,
Peter G.

 

[xiaoB]

Maybe the book answer was wrong!

 

[Peter G.]

Yes, I think so!

So, what is right: (2x + 1)² then, therefore, 2 + 1 = 3, and 3² = 9

or: (2x + 1)² = (2x + 1) (2x + 1) = 4x² + 4x + 1, then, sub 1?

Thanks,
Peter G.

 

[xiaoB]

Whatever !

 

[Peter G.]

Ok, thanks for the help!