SOLUTION: A square has all its edge lenghts increased by 3cm. This makes a new square with twice the area of the old one. What was the area of the old square. i was wondering if you c

Question 267551: A square has all its edge lenghts increased by 3cm.
This makes a new square with twice the area of the old one.
What was the area of the old square.
i was wondering if you could show me how this is worked out
it is to help my daughter for school thanks Valerie
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A square has all its edge lenghts increased by 3cm.
This makes a new square with twice the area of the old one.
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Call the original side length s
The original area is s^2.
(s+3)*(s+3) = 2s^2
s^2 + 6s + 9 = 2s^2
s^2 - 6s - 9 = 0
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Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=72 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 7.24264068711928, -1.24264068711928. Here's your graph:

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Ignore the negative answer
cm
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It's probably messier than you expected.

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