Question

Within 11 years, the age of Peter will be half the square of the age he was 13 years ago. Calculate the current age of Peter. Reject the extraneous solution.

Answer 1

21

ctto JBarnum

Explanation:

P+11=(1/2)(P-13)^2

P+11=(1/2)(P^2-26p+169)

2(P+11)=(1/2)(2)(P^2-26p+169)

2P+22=P^2-26p+169

0=P^2-28p+147 ( -7 and -21)

(P-7)(P-21)=0

P=7,21 (cant be 7 as 13 years from 7 is negative so peter is 21)

checking:

21+11=32

32=(1/2)(21-13)^2

32=(1/2)(8)^2

32=(1/2)64

32=32

correct