Question

f(x) = 4x + 5
h(x) = √5x - 4
Find: (hf)(4)

Answer 1

Those are the choices
√17 84
5 25

Answer 2

Sweeeeet I love these.. Hold up

Answer 3

ok i have a lot of them lol

Answer 4

If i get this wrong i'm gonna feel bad :(

Answer 5

This is a hard one

Answer 6

lol well i gave choices

Answer 7

If i take my best guess will you be mad at me ???? :)

Answer 8

lol is it even close to any of the choices?

Answer 9

For clarification, is your h(x) equation \[\sqrt{5x-4}\] or \[\sqrt{5x}-4\]

Answer 10

Either way, the basic principle here is that you have two functions multiplied together and you substitute '4' in every place you have an 'x'.

Answer 11

its over the whole thing

Answer 12

and i tried it and i got 25

Answer 13

I do not see how that is possible. Could you please show me how you got it?

Answer 14

i did f(4)=4(4) +5
16+5 =21
then i did
h(4) = sqaure root thing 5(4)-4 then sqaure root 16 = 4 then added 21 and 4

Answer 15

You are right all the way up to the last step. You are not being asked to solve (f+h)(x), you are given (f*h)(x)

Answer 16

so 21 * 4?

Answer 17

Yes.

Answer 18

oh!! so 84 yay i got it

Answer 19

Good job. :)

Answer 20

what about this f(x) = 2x - 7
g(x) = -4x2 - 6x
Find: g(f(x))


-8x3 + 16x2 + 42x -8x2 - 12x - 7
-16x2 + 100x - 154 20x2 + 30x

Answer 21

As I'm sure you have guessed, this one does not have a value for 'x' so you won't be able to solve to completion. However the same principle applies only this time you are putting the 'f(x)' into 'g' as the 'x' component.

Answer 22

That was my first guess...

Answer 23

What if we made an example and said, f(x)=4, find g(f(x))? What would you do?

Answer 24

i got -8x3 + 16x2 + 42x

Answer 25

How?

Answer 26

(-4x^2 -6x)(2x-7)
-8^3 +28x^2 -12x^2 +42
-8^3 +16x^2 +42

Answer 27

You are not multiplying these two expressions.

Answer 28

If I gave you g(x)=4x+3, x=2, and asked you to solve this, how would you do it?

Answer 29

You would plug the 2 in everywhere you saw an 'x' and work the expression.

Answer 30

the one i just typed was the answer to this f(x) = 2x - 7
g(x) = -4x2 - 6x
Find: g(f(x))

Answer 31

That is exactly what you are asked to do here, only instead of '2' you must plug in '2x-7'

Answer 32

I would not agree that 8x^3+16x^2+42 was the answer.

Answer 33

im confused.......

Answer 34

Okay, you are given g(x) = -4x2 - 6x, f(x) = 2x - 7, and asked to find g(f(x)). Let's try a mental exercise before we attack this problem.
What if instead I gave you g(x) = -4x^2-6x and told you that f(x)=2, then asked you to find g(f(x)), how would you approach solving this?

Answer 35

g(f(2)=-4(2)^2-6(2)

Answer 36

Yes! The right idea, off a little on notation but we can handle that.

Answer 37

So now the problem you have, g(x) = -4x2 - 6x, f(x) = 2x - 7, and asked to find g(f(x)), do the same thing only instead of plugging in the '2' you will now use '2x-7'

Answer 38

I think you need to go a little "slower" on her.

Answer 39

g(f(2x-7))?!!?!?!?

Answer 40

I don't think so, she has the idea and is clearly capable of understanding. We just need to make that connection for her on this and she's nailed it.

Answer 41

Exactly, although the proper notation would be g(2x-7) and so you would plug '2x-7' in everywhere there is an 'x' in your 'g' expression.

Answer 42

Or are you trying to nail it??

Answer 43

fuknut