Geometrical shapes with an unknown

[Femme_physics]

Homework Statement

http://img857.imageshack.us/img857/3200/thedrawing00.jpg


In a rectangle ABCD a square is built, EFGD, and a right triangle BMF, as described in the drawing.
Given:
DC = 60 cm
BC = 40 cm
The sum of the area of the square and the triangle is 784 cm2

Calculate x (find both answers).

The Attempt at a Solution

I built the equation of their area using x. As I solve the final quadratic am not getting the right figures from some reason.

http://img709.imageshack.us/img709/7970/areaxx1.jpg

 

[QuarkCharmer]

Ok: I work it out to 3x^2 - 100x + 832 = 0. I think you just let -x times -x = -x^2 for some reason.

 

[Femme_physics]

Thanks, yes :) Just made a silly mistake *slaps forehead*

Much appreciated.