Question 68989
L*W=30
L=W+4 thus 
(W+4)W=30
W^2+4W=30
W^2+4W-30=0
USING THE QUADRATIC EQUATION WE GET
X=(-B+-SQRT[B^2-4QC])/2A
X=(-4+-SQRT16-4*1*-30])/2*1
X=(-4+-SQRT16+120])/2
X=(-4+-SQRT136)/2
X=(-4+-11.66)/2
X=(-4+11.66)/2
X=7.66/2
X=3.83M IS THE WIDTH. 
THUS THE LENGTH IS 
L*3.83=30
L=30/3.83
L=7.83M IS THE LENGTH
PROOF
3.83*7.83=30
30=30