SOLUTION: The length of a rectangle is 10cm less than 3 times its width. If the perimeter of the rectangle is at most 180 cm, find the greatest possible length of the rectangle.

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Question 113347: The length of a rectangle is 10cm less than 3 times its width. If the perimeter of the rectangle is at most 180 cm, find the greatest possible length of the rectangle.
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
LENGTH=3W-10
180=(3W-10)W
180=3W^2-10W
3W^2-10W-180=0
USING THE QUADRATIC EQUATION WE GET:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
W=(10+-SQRT[10^2-4*3*-180])/2*3
W=(10+-SQRT100+2160])/6
W=(10+-SQRT2260)/6
W=(10+-47.54)/6
W=(10+47.54)/6
W=57.54)/6
W=9.59 ANSWER.
W=(10-47.54)/6
W=-37.54/6
W=-6.26 ANSWER.