Question

If the difference between the length and breadth of a rectangle is 20m and its area is 400m2 Calculate The perimeter of the rectangle

Answer 1

given

l-b=20
lb=400

from relation
${(a + b)}^{2} = {(a - b)}^{2} + 4ab$
substitute given values (take a=l, b=b)
${(l + b)}^{2} = {(l - b)}^{2} + 4lb$
${(l + b)}^{2} = {20}^{2} + 1600$
$l + b = \sqrt{400 + 1600} = \sqrt{2000}$
we need perimeter
2(l+b)= 2√2000

Answer 2

Answer is given below:------

given

l-b=20
lb=400

from relation 
{(a + b)}^{2} = {(a - b)}^{2} + 4ab(a+b)2=(a−b)2+4ab 
substitute given values (take a=l, b=b)
{(l + b)}^{2} = {(l - b)}^{2} + 4lb(l+b)2=(l−b)2+4lb 
{(l + b)}^{2} = {20}^{2} + 1600(l+b)2=202+1600 
l + b = \sqrt{400 + 1600} = \sqrt{2000}l+b=400+1600​=2000​ 
we need perimeter
2(l+b)= 2√2000