Jodancer4404: how do I find the value for x, in mathematical functions that are equal to zero?
f(x)=0 -2x^2+5x+9
I think that you mean
f(x)= -2x
2 + 5x + 9
find x when f(x)=0
If it was easy then you would just factorise first.
but to factorise manually you need to find 2 numbers that multiply to -2*9=-18 and add to +5 and these numbers are effectively impossible to find.
so
we could do it by completing the squares, or the more usual way is to use the quadratic forumula.
here's the formula
http://www.youtube.com/watch?v=O8ezDEk3qCg
+118654 
