Question

Let f(x)=3x+5 and g(x)= -4x+7. Find (fog)(-4)
The answers given are:

A. 35
B. 74
C. -7
D. 23

Answer 1

Multiply f(x) by g(x)
and then put x=4

Answer 2

wait so I would do: 3x+5 * -4x+7?

Answer 3

Input function g into function f, and then replace x for -4.
(fog)(x)= -4(3x+5)+7
= -12x-20+7 = -12x-13
(fog)(-4) = -12(-4)-13 = 35

Answer 4

Thank you so much! I have more questions like this and I'm seriously hating it right now lol. Thank you for explaining it to me!

Answer 5

Happy to help! Good luck!

Answer 6

What about for adding though??

Answer 7

I have another one and it says: let f(x)= 4x-5 and g(x)= 3x+7. Find f(x)+g(x) and state its domain???

Answer 8

Do you know what domain of a function means? I am guessing thats where the confusion is?

Answer 9

That would mean all real numbers right?

Answer 10

The confusion is more on how to write everything and then solve it. With these questions, there's an adding, dividing, and a multiplying one.

Answer 11

I see, yes, this is just simple adding the functions. So, 4x-5+3x+7 = 7x+2. So, domain would be all real numbers. Correct

Answer 12

OHH!! okay so for adding I would just add the both of them! Okay thank you!

Answer 13

Yes, fog is different. Read fog as f as a function of g, just like f(x) is f as a function of x. Hope this clarifies.

Answer 14

It definitely does. Thank you.