Question 85354
Given a triangle with sides:
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3x + 7
4x - 9
5x + 6
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To find the perimeter of this triangle, just add the three sides together. You can do this
by adding the columns above.  That is, add 3x + 4x + 5x and you get 12x.  Next add the second
column ... +7 -9 +6 = +4.
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As a result of these additions you can say that the perimeter of the triangle is 12x + 4.
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Hope this helps you understand how to do this problem.