Posted by **Shawn** on Sunday, October 12, 2008 at 4:41pm.

f(x) = 1/(x+7)+15/(x-8). Find all a for which f(a)=f(a+15).

I understand this so far

f(a)=f(a+15)

1/(7+a) + 15/(a-8) = 1/(a+22) + 15/(a+7)

I have multiplied the LCD of (a-8)(a+7)(a+22)by both sides with no luck.

This is a multiple choice question

a.) -161/8

b.) 120/7

c.) 161/7

d.) -17

I have the answer as

Responses

Math problem still stuck - Ryan, Sunday, October 12, 2008 at 4:05pm

Just plug in the values since it's multiple choice.

Math problem still stuck - Shawn, Sunday, October 12, 2008 at 4:12pm

When I plug in the values what am I looking to find?

Math problem still stuck - bobpursley, Sunday, October 12, 2008 at 4:20pm

If you want to plug in, plug in the answer for a to see if both sides are equal.

Math problem still stuck - Ryan, Sunday, October 12, 2008 at 4:21pm

you want 1/(7+a) + 15/(a-8) = 1/(a+22) + 15/(a+7), your second equation, to be true, so you true the four values of a given in the equation and if both sides are equal, you've found it.

Math problem still stuck - Ryan, Sunday, October 12, 2008 at 4:22pm

*try not true

Math problem still stuck - Shawn, Sunday, October 12, 2008 at 4:32pm

So you are saying that it is none of the multiple choice answers of -161/8,

120/7, 161/7, or -17

?

- Math check 3 -
**bobpursley**, Sunday, October 12, 2008 at 4:44pm
I don't think Ryan said the answers is none. He said try them to see if both sides are equal. I think it was me a couple of threads ago that I told you to go through it once more to see if it works, that I did it in my head and didn't get any of the answers.

I don't know what is the problem here. If you want to plug the given answers in for a, do it. If not, don't.

- Math check 3 -
**Damon**, Sunday, October 12, 2008 at 5:03pm
I get -21 1/16

In other words none of the above.

- Math check 3 -
**j**, Sunday, January 10, 2010 at 10:12pm
(a+15)(a+7)

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