SOLUTION: Geomatry. If the sides of a square are decreased by 2cm, the area is decreased by 36cm^2

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Question 92555: Geomatry. If the sides of a square are decreased by 2cm, the area is decreased by 36cm^2
Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
Let x be the length of the side of the original square. Therefore, the area of the original
square is x^2.
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Now take 2 cm off each side of the original square. That means that the length of the side
of the new square is x-2 cm. You square this to get the area of this new square. So the
area of the new square is:
.
%28x-2%29%5E2+=+x%5E2+-4x+%2B+4
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The problem then says that the difference between the original area %28x%5E2%29 and the new
area %28x%5E2+-+4x+%2B4%29 is 36 cm^2. Setting this up as an equation we have:
.
x%5E2+-+%28x%5E2+-+4x+%2B4%29+=+36
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Since the parentheses are preceded by a minus sign, you can remove the parentheses
by changing the signs of the terms within the parentheses. This leads to:
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x%5E2+-+x%5E2+%2B+4x+-+4+=+36
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Note that the x%5E2 terms cancel each other due to their difference in signs. So
they drop from the equation which then becomes:
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4x+-+4+=+36
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Get rid of the -4 on the left side by adding +4 to both sides. This reduces the equation to:
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4x+=+40
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Solve for x by dividing both sides by 4 to get:
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x+=+40%2F4+=+10
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So the length of each side of the original square is 10 cm.
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And the length of each side of the new square is 10 - 2 or 8 cm.
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Check. The area of the original square is 10*10 = 100 cm^2. The area of the new square is
8 * 8 = 64 cm^2.
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The difference in their areas is 100 cm^2 - 36 cm^2 = 64 cm^2.
.
Hope that the answer you were looking for is in here somewhere. This will probably
give you the process you can use to solve this problem.