If we are still talking about "P(n,5) = 20 P(n,3)", then both your answers are wrong.Didnt the problem reduce to solving the quadratic ?(As shown by Grandad...)
. Solve this quadratic...
Always verify your answers by substituting it back in the original equation and verify if your answer is right...
Hello ImKo -
I really think you need to do some work on solving quadratic equations. Your answers using the quadratic formula were incorrect, because you missed a minus sign. But before using the formula, you should always try to factorise - and is one of the easiest quadratic expressions to factorise.
Can you do it?
It will look like this:
This will give you two possible values of , only one of which is appropriate - see mr fantastic's hint.
Grandad