Question

Please help
1) f(x) = x^2 + 3; g(x) = x - 7
which expression is equal to (f + g)(x)?
x^2-14x+52
x^2-4
x^3-7x^2+3x-21
x^2+x-4
2) f(x) = 4x - 1; g(x) = 5x^2
which expression is equal to (fog)(x)?
5x^2 + 4x - 1
20x^2 - 1
80x^2 - 40x + 5
20x^3-5x^2

Answer 1

(f+g)(x) = f(x)+g(x)=(x^2 + 3) + (x - 7)

Answer 2

3) f(x) 3x-9; g(x) = x-4
what is the value of (gof)(5)
5
6
2
9
4) what is the value of f(-4)?
f(x) = {-10 if x<-5
{ x^3 if-5≤x≤2
{ 2x+4 if x>2
-12
-64
-10
-4

Answer 3

(fog)(x)=f((g(x))
which means let x=g(x)
so substitute the entire g(x) function into f(x)

Answer 4

(gof)(5)=g(f(5))
which means do f(5), where x= 5

then substitute this value into g(x) where x=f(5)

Answer 5

cant you just tell me what the answer is for all of them?

Answer 6

please help @zepdrix

Answer 7

if you put some effort into attempting them then sure

Answer 8

I don't know how to d this?

Answer 9

if I had f(x)=3x
then said I want f(4)
I would let x=4 to get

f(4)=3(4)
f(4)=12

so if I had f(x)=3x
g(x)=5x

then

(f+g)(x)=f(x)+g(x)=3x+5x
so this means I add the functions together

if I have

(fog)(x)=f(g(x))
we always start from right to left, so you do g(x) first, then substitute this into f(x) where x=g(x)


we know that g(x)=5x
so now we let x=5x
I get
(fog)(x)=f(g(x))=f(g(x))
f(5x)
so f(5x)=3(5x)=15x


if I had (gof)(x)
we would do g(f(x)) instead

Answer 10

The topic here is "composite functions."

You might get more help, faster, if you would (1) post only one question at a time, (2) share whatever you have done on a given problem, and (3) not ask for answers without first having put some effort of your own into solving problems here.

Answer 11

Ok thanks!

Answer 12

To obtain (f+g)(x), merely add f(x) and g(x) together. Try it.