let l the length and w the width of the rectangle. we have l=2w-1 the area is l x w = (2w-1)w=21^2=441
so 2w^2-w-441=0 solving the equation we have w=15.102 m (we keep the possitive value for w, since
a nagative value cant be) so l=2*15.102 -1 = 30.204 -1=29.204
check 15.102 x 29.204 = 441 approx = 21^2