Let the shorter side of the rectangular field = x m.
Then its longer side = x + 30 m
The diagonal of a rectangle is also the hypotenuse of the lower triangle Here the diagonal = x + 60
∴ By Pythagoras theorem
(side)2 + (side)2 = (hypotenuse)2
(x + 30)2 + x2 = (x + 60)2
x2 + 60x + 900 + x2 = x2 + 120x + 3600
x2 - 60x - = 0
x2 - x + 30x - = 0
x(x - ) + 30(x - ) = 0
(x - )(x + 30) = 0
x - = 0 or x + 30 = 0
x = or x = -30 But 'x' can't be negative.
∴ x = m
i.e , the shorter side x = 90 m Longer side x + 30 = +30=m