need help quadratic equations

My answer was:

ABC = x * (x-4)
DEF = (x - 2) * (x + 2x)
(x * (x-4)) + ((2x + x) * (x - 2)) = 36cm²
(x² - 4x) + (3x² - 6x) = 4x² - 10x 4x² - 10x = 36cm²
4x² - 10x - 36 = 0cm²
(4x² - 10x - 36) / 2 = 0
(4x² - 10x - 36) / 2 = 2x² - 5x - 18
2x² - 5x - 18 = 0
x = 4.5 or x = -2

AB = 4.5cm

What am I missing? I'm sure this is correct I've been over it loads.

Somebody please help. Thank you if you reply.

Looks ok to me. If you're unsure sub x=4.5 and check the areas of the 2 rectangles add up to 36.

I added

ABCDEF = 36cm²
4x² - 10x = 36cm²
4(4.5²) - 10(4.5) = 81 - 45 = 36cm²
x = 4.5cm
AB = x
AB = 4.5cm

still no marks?? any idea? ik mathswatch can be useless sometimes but im OCD about getting 100% lmao

I got the same answer as you.

Answer is right but its mathswatch formatting. ABC is a triangle.
It may be it wants some of the -b+/-sqrt() formatting to show that the calculation is correct, but (thankfully) I'm not a mathswatch expert so I'll bow out.