Math problem still stuck
posted by Shawn .
Let f(x) = 1/(x+7)+15/(x8). Find all a for which f(a)=f(a+15).
I understand this so far
f(a)=f(a+15)
1/(7+a) + 15/(a8) = 1/(a+22) + 15/(a+7)
I have multiplied the LCD of (a8)(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

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

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

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

you want 1/(7+a) + 15/(a8) = 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.

*try not true

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