Thread: Need Help. Confusing Equation

The gievn equation is: -

P+Q = a (P-Q)

How can get this form: Q = {(a-1) / (a+1)}P from the above equation?

You'll need to get all terms with a "Q" in them on one side.
P + Q = aP - aQ
P + aQ + Q = aP
aQ + Q = aP - P
Factor!
Q(a + 1) = P(a - 1)
Divide by (a + 1)