# Math problem still stuck

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Let 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

• Math problem still stuck -

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

• Math problem still stuck -

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

• Math problem still stuck -

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

• Math problem still stuck -

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 -

*try not true

• Math problem still stuck -

So you are saying that it is none of the multiple choice answers of -161/8
120/7 161/7 or -17
?