Question 995660
i think i figured it out.


first time for everything and this is the first time i saw one like this.


but i got 20 so i must be doing something right.


i think.


you have 2 functions.


f(2x+1) = 2x^2 - 1


g(x) = 3 + x


you want to find the value of gof(7).


gof(x) is equal to g(f(x)).


so was start with f(x).


but it's not f(x), it's f(2x+1)


in order to make that f(7), we have to find a value of x that makes 2x+1 = 7


that value of x = 3.


you have to replace x with 3 in the function.


f(3) = 2x^2 - 1 becomes f(3) = 18 - 1 = 17


you have f(3) = 17.


now you want to take g(x) = 3 + x and replace x with 17.


you will get g(17) = 3 + 17 which then becomes 20.


scary problem, but the whole idea appeared to be that, in order to get f(7), you needed to find the value of x that made 2x+1 = 7.


that value of x was 3).


so f(7) means you have to replace 2x+1 with 7 and that only happens when x = 3.


so f(2x+1) = 2x^2 - 1 becomes f(3) when 2x+1 = 7.


like i said, i never saw one like this before, but i got the right answer so i'm reasonably satisfied i interpreted it correctly.