math
posted by aldwin on .
In 11 years, the age of Russel will be half of the square of the age he was 13 years ago. Find his present age.

x + 11 = ( 1 / 2 ) ( x  13 ) ^ 2
x + 11 = ( 1 / 2 ) ( x ^ 2  2 x *13 + 13 ^ 2 )
x + 11 = ( 1 / 2 ) ( x ^ 2  26 x + 169 )
1 / 2 ( x ^ 2 )  13 x  x + 169 / 2  11 = 0
( 1 / 2 ) x ^ 2  13 x  x + 169 / 2  22 / 2 = 0
( 1 / 2 ) x ^ 2  13 x  x + 147 / 2 = 0
The exact solutions are:
7
or
21 
In 11 years, the age of Russel will be half of the square of the age he was 13 YEARS AGO.
For that reason present age = 21