P=2(L+W)
A=LW
given
P=62
62=2(L+W)
divide 2
31=L+W
minus W
L=31-W
sub into other one
A=LW
A=(31-W)(W)
228=31W-W^2
times -1
W^2-31W=-228
add 228 both sides
W^2-31W+228=0
factor
what 2 numbers multiply to get 228 and add to get -31
-19 and -12
(W-19)(W-12)=0
set to zero
W-19=0
W=19
W-12=0
W=12
sub back
L=31-W
L=31-12
L=19
or
L=31-19
L=12
the doorway is 12in by 19in
