SOLUTION: a woman is 3times older than her daughter 8years ago the product of thier age was 112. find their age now

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Question 970976: a woman is 3times older than her daughter 8years ago the product of thier age was 112. find their age now
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
a woman is 3times older than her daughter 8years ago the product of thier age was 112. find their age now
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1 time older = 2x as old
2 times older = 3x as old
3 times older = 4x as old
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W = 4D
(W-8)*(D-8) = 112
(4D - 8)*(D - 8) = 112
(D - 2)*(D - 8) = 28
D^2 - 10D - 12 = 0
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B-10x%2B-12+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-10%29%5E2-4%2A1%2A-12=148.

Discriminant d=148 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--10%2B-sqrt%28+148+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-10%29%2Bsqrt%28+148+%29%29%2F2%5C1+=+11.0827625302982
x%5B2%5D+=+%28-%28-10%29-sqrt%28+148+%29%29%2F2%5C1+=+-1.08276253029822

Quadratic expression 1x%5E2%2B-10x%2B-12 can be factored:
1x%5E2%2B-10x%2B-12+=+%28x-11.0827625302982%29%2A%28x--1.08276253029822%29
Again, the answer is: 11.0827625302982, -1.08276253029822. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B-10%2Ax%2B-12+%29

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Daughter's age now =~ 11.0827 years
Mother's age =~ 44.3308 years
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The solution is not in integers because the author of the problem thinks "3 times older" = 3 times as old.
The author should be a politician, a job that does not require him/her to know what he's talking about.