Question 845367
area = 56
l*b = 56 
perimeter = 30
2(l+b) = 30 
l+b = 15
squaring on both sides 
(l+b)^2 = 225
{{{l^2+b^2 + 2lb = 225}}}
{{{a^2+b^2 = ((a+b)^2 + (a-b)^2)/2}}}
{{{((l+b)^2 +(l-b)^2)/2 +2lb= 225}}}
{{{((15)^2+ (l-b)^2 + 4*56)/2 =225}}}
{{{225+(l-b)^2 + 224 =450}}}
{{{(l-b)^2+ 449 = 450}}}
{{{(l-b)^2 =1}}}
{{{l-b = 1}}}