The quadratic equation would be formed in this way...
length X breadth=area
x(x+7)=170
x^2 + 7x =170
x^2+7x-170=0
x^2 + 17x-10x-170=0
x(x + 17) -10(x+17)=0
(x+17)(x-10)=0
either x=-17(rejected as it is negative) or x=10 meters
therefore the sides are 10 and 17 meters