Question 981935
let length be x

area = l*b

breadth = 420/x


{{{(x+7)((420/x)-5))=420}}

Simplify

{{{(x+7)((420-5x)/x) =420}}}


(x+7)(420-5x) = 420x


{{{420x-5x^2+420*7-35x=420x}}}

{{{-5x^2-35x+420*7=0}}}

/-5

{{{x^2+7x-588=0}}}


(x-28)(x+21)=0

x=28 OR -21

length = 28m & breadth = 21 m