Suppose a rectangle has an area of 90m^{2} and the sides are x+1 and x+2. Find the dimensions of the rectangle.
(x+1)·(x+2)=90
x^{2}+3x+2=90
x^{2}+3x-88=0
(x+11)·(x-8)=0
x+11=0; x=-11
x-8=0; x=8
The sides are 9m and 10m long.

A father's age is equal to the square of the age of his son. In 15 years time the father's age will be twice that of his son. How old are both of them now?