SOLUTION: Lauren is 4 years older than David. The product of their ages is 45. How old is Lauren?

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Question 964106: Lauren is 4 years older than David. The product of their ages is 45. How old is Lauren?
Found 2 solutions by macston, tenkun:
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
.
L=Lauren's age; D=David's age=L-4
LD=45 Substitute for D
L%28L-4%29=45
L%5E2-4L=45 Subtract 45 from each side.
L%5E2-4L-45=0
%28L-9%29%28L%2B5%29=0
L-9=0 or L%2B5=0
L=9 or L=-5
ANSWER: Lauren is 9 years old.
CHECK:
D=L-4=9-4=5 David is 5 years old.
L*D=45
9*5=45
45=45

Answer by tenkun(12) About Me  (Show Source):
You can put this solution on YOUR website!
let David's age = x
Lauren's age = x+4
Given that product of their ages is 45
x*(x+4) = 45
x^2 +4*x= 45
x^2+ 4*x -45=0
x^2+9*x- 5*x-45=0
x*(x+9)- 5*(x+9)=0
(x+9)*(x-5)=0
x=-9 negative
so x=5
Hence David's age=5
Lauren's age= 5+4=9