Arectangles plot of ground is 30 meters longer than it is wide. its area is 10,000 square meters

A = W· L
10,000 = W ( W +30 ) = W² + 30 W
W² + 30 W - 10,000 = 0
W = 
L = 86.12 + 30 = 116.12
Width of a plot is 86.12 m and lenght is 116.12 m.
Check : A = 116.12 · 86.12 ≈ 10,000

The linear equation is: y=ax+b