Question

Victor is y years old.
His brother Fred is four years old than Victor.
The product of their ages is 780.
(a) Set up an equation to represent this information.
(b) Solve your equation from (a) to find Victor’s age.

Answer 1

(a) Victor = y

Fred = y + 4

Product = 780

=> y(y+4) = 780

=> y^2 + 4y = 780

(b) y^2 + 4y - 780 = 0

=> y^2 + 30y - 26y - 780 = 0

=> y(y + 30) - 26(y + 30) = 0

=> (y - 26)(y + 30) = 0

=> y = 26, -30

As age ≠ negative, Victor = 26 years.

Answer 2

Answer:

a) Fred's age =y+4 yrs.

y*(y+4)=780

b) y*(y+4)=780

y sq.+4y =780

y sq. +4y -780=0

y sq. -26y+30y-780=0

y(y-26)+30(y-26)=0

(y-26)(y+30)=0

y-26=0

y=26

y+30=0

y=-30

so vector's age = 26 years we cannot take his age -30 because age can never be negative