Posted by **Lori** on Friday, March 28, 2008 at 5:01pm.

Can someone tell me what I am doing wrong? Do I need to graph this to get the right answers?

Problem:

Find the requested value.

f(3) for f(x)

3x+1, if x<1=3(3)+1=10

3x, if 3<=x<=8=3(3)=9

3-5x, if x>8=3-5(3)=-12

- Algebra -
**Damon**, Friday, March 28, 2008 at 5:30pm
Only the middle one counts as I understand your question.

x is not less than one. It is three

When x is 3, then 3<= x

x is not more than eight,. It is three.

so for x = 3 , f(x) = 3 x = 9

- Algebra -
**Lori**, Friday, March 28, 2008 at 5:39pm
But the reason I am having trouble is because the middle one does not work.

The first part works, but the second part does not.

3<=x<=8=3(3)=9

8=3(3)=9 (?)

- Algebra -
**Damon**, Friday, March 28, 2008 at 6:45pm
That just means that between x = 3 and x = 8 (including 3 and 8)

You can use

y = 3 x

if x were 4, you could say y = 3*4 = 12

BUT

if x is 9 , you are not allowed to use this relation and have to use some other one.

In this particular case, you would use

y = 3 - 5x

if x were 9, which is greater than 8

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