# Math

posted by .

f(4b)=4x^2+5x-5

f(x+1)=8x^2+x-3

f(-x)=8x^2+x-3

*I think that the first two use F.O.I.L but i still cant get it

• Math -

I'm afraid I do not catch your question.

Are you supposed to find f(4b) when f(x)=4x^2+5x-5? Or are you supposed to find f(x) when f(4b)=4x^2+5x-5. The second option does not make sense because the expression f(4b) should not leave any trace of "x" when x=4b.

• Math -

x=4b sorry

• Math -

Would the question then be:
1.
If f(x)=4x^2+5x-5, find f(4b).
In this case,
f(4b)= 4(4b)² + 5(4b) -5
= 4(16b²) + 20b -5
= 64b² + 20b -5

• Math -

Okay thank you that really makes more since your a lifesaver! Do you know how to do number 2 and 3 that you could walk me through too? I have literally tried them 11 times and it still says they are wrong

• Math -

2.
First step: write down the function in terms of x:
f(x)=8x^2+x-3

Then substitute x by what is in the parentheses (x+1) in this case. Don't forget the parentheses everywhere you make a substitution:
f(x+1)=8(x+1)² + (x+1) - 3
Expand and collect terms as required:
f(x+1)
=8(x+1)² + (x+1) - 3
=8(x²+2x+1) + x+1 -3
=8x² + 16x + 8 +x+1 -3
=8x² + 17x + 6

Proceed the same way for number 3. Post for checking if necessary. The answer is 8x²-x-3.

## Similar Questions

1. ### English

Regarding the writer's strike, what are two valid reasons to support it: I can only think of one. The writer's should be adequately compensated. Would a second one have to do with royalties?
2. ### English

1. Cheer up, guys. (What other expressions can we use instead of 'guys'?

Suppose you are in the market for a new home and are interested in a new housing community under construction in a different city. a) The sales representative informs you that there are two floor plans still available, and that there …
4. ### trigonometry

(3^m)(5^(m+1))=12^(2m-1) not sure how to solve this but I think you use natural logs?
5. ### math-calculus

30/x^2-25 = 3/x-5-2/x+5 i be left with 30 = 3x^2-75-2x^2+50 i not sure what to do?
6. ### Algebra

the phone company has two plans for cell phones. the first plan calls for a monthly fee of 35.00 with unlimited calling. The other plan is a monthly fee of 15.00, with a 0.50 fee for every minute over 100 used in a month. What is the …
7. ### math

Now suppose Streak-Shooting Shelly has moved to mars. Shelly is still adjusting to Mars. Her overall performance is down, but she still shoots better when she has just made a shot. Suppose Shelly has a 60% probability of making the …
8. ### math

Now suppose Streak-Shooting Shelly has moved to mars. Shelly is still adjusting to Mars. Her overall performance is down, but she still shoots better when she has just made a shot. Suppose Shelly has a 60% probability of making the …
9. ### English

1. Do you know? + Can he play the piano? 2. Do you know if/whether he can play the piano?
10. ### Math

Jason won some goldfish at the state fair.during first week,1/5 of them died, and during second week, 3/8 of those still alive are the end of the first week died.what fraction of the original goldfish were still alive after two weeks?

More Similar Questions