# Having trouble with finding a Quadratic Expression

I am having trouble trying to work out a quadratic expression for uni, being a external student its hard to find help.

My problem is

Perimeter = 1000m Part 1 Solve L in terms of w in regard to the perimeter

I worked out $l = \frac{P - 2w}{2}$

Part 2 Substitute l to find out the area A = lw

$A = \frac{P-2w}{2}\times w$ now I need to turn that formula into a Quadratic expression. When I try and simplify the above equation and test it with the values l=250 w=250 so that p=1000 It doesn't work.

I simplified it to $A = \frac{1000-2w}{2} \times w = \frac{1000-2w^2}{2}$

But when i check it it does not work out. Any help to get me to a quadratic would be awesome thanks

-
Algebra error: you didn’t multiply in the $w$ correctly. You should have $$\frac{1000-2w}2\cdot w=\frac12(1000-2w)w=\frac12(1000w-2w^2)=500w-w^2\;.$$ – Brian M. Scott Apr 5 '12 at 8:39
thanks I will try it again and see how I go – Ashley Hughes Apr 5 '12 at 22:14
Thanks for the help @BrianM.Scott ended up with $(-w+500)(w+0)$ as my quadratic after much swearing thanks again – Ashley Hughes Apr 5 '12 at 23:23