Question

Given that f(x) = 2x + 1 and g(x) = –5x + 2, solve for f(g(x)) when x = 3.

Answer 1

I feel like I know how to solve but I'd like to be sure!

Answer 2

for f(g(x)) just substitute the g(x) in place of x inside f(X)

OK ?

Answer 3

after that calculi this for x=3

Answer 4

So f(x)=2(-5x+2)+1?

Answer 5

this wan being f(g(x)) not f(x) ,ok ?

Answer 6

so than is right just now you need calculi it

Answer 7

I'm sorry what?

Answer 8

@Loser66

Answer 9

this is above right for f(g(x))

Answer 10

I'm lost.

Answer 11

@johnweldon1993 would you mind helping me out? @jhonyy9 with all due respect, sir, your english isn't too great.

Answer 12

f(x) = 2x + 1
g(x) = -5x + 2

f(g(x)) when x = 3

G in inside the 'f' function so we focus on that first....we can plug in the x = 3 into the g(x) equation we have

g(x) = -5x + 2
so
g(3) = -5(3) + 2
= -15 + 2
= -13

Answer 13

Now..we plug in what we got as a result from g(3)...and plug it into f(x)

we received an answer of -13 from g(3)...so we plug in that -13 into f(x) wherever we see an 'x'

Answer 14

so f(x) = 2x + 1

f(g(3)) = 2(-13) + 1
= -26 + 1
= -25

Answer 15

Ahh okay! I got -13 at some point but didn't know how to carry on. Thank you so much!

Answer 16

Not a problem :)

Answer 17

And just 1 more thing...what @jhonyy9 was doing was also correct.

Notice how I upfront plugged in x = 3....what jhonny9 was doing was going through the algebra first...and then plugging in the 3

so for that...he took the fact that

g(x) = -5x + 2

And he plugged THAT into f(x) wherever there was an 'x'

since f(x) = 2x + 1

That made it

f(g(x)) = 2(-5x + 2) + 1
= -10x + 4 + 1
= -10x + 5

Now when you plug in x = 3 you get

-10(3) + 5
-30 + 5
-25


Same as we received as plugging it in first

*Just wanted to clear that up :)