Question

how do you find f(x) = x2 + 3x and g(x) = 2x – 2

Find (f o g)(-2+x) ?

Answer 1

These are two distinct functions, one is a parabola and the other one is a linear function.

And what do you mean by f o g?

Answer 2

f of g.. it's composition.

Answer 3

\(f(g(x))\) like this?

Answer 4

yes!

Answer 5

Okay, let's start with the basic, so you can fully understand it, because you'll be using it a lot in calculus :)

E.g.: We have, let's say \(f(x)=4x\) and I'm asking you to find \(f(5)\); THIS mean that you have to replace \(x\) by 5.

Answer 6

okayy i get that

Answer 7

So, you have \(f(g(x))\) that mean to replace \(x\) by _______?

Answer 8

Good :)

Answer 9

by the 5?

Answer 10

No no, look at above, 5 is what is in the parentheses of f.

Answer 11

Let me give you few more examples;

Answer 12

by the 4x?

Answer 13

\(f(x)=67x^2; \text{find} f(57)\) Replace \(x\) by 57 to find \(f(57)\)
\(f(x)=2x; \text{find} f(z)\) Replace x by \(z\) to find \(f(z)\)

And it's not 4x, try again :)

Answer 14

oh my gosh! im so confused haha. your gonna make me work for the answer aren't you? :)

Answer 15

Yes :)

Answer 16

Let's try some few more :D

\(f(x)=5x^2-4x+20\)

Find \(f(90)\)

Replace x by 90 to find the solution.

Answer 17

So basically, you replace x by whatever is in the parentheses and evaluate :D

Answer 18

So when you are asked to find \(f(g(x))\), you replace x by _____? :D

Answer 19

so the question you just gave me, is the answer 40,160?

Answer 20

Uh, they were only example xD

Answer 21

So when you are asked to find \(f(g(x))\), you replace x by g(x)!