SOLUTION: The height of a triangular flag is 5 inches more than twice its base. the flag is made of 84 square inches of fabric , what are the dimensions of the flag?

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Question 1165650: The height of a triangular flag is 5 inches more than twice its base. the flag is made of 84 square inches of fabric , what are the dimensions of the flag?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The height of a triangular flag is 5 inches more than twice its base.
the flag is made of 84 square inches of fabric,
what are the dimensions of the flag?
:
let b = the width of the base (b)
then
(2b+5) = height (h) of the flag
:
Area of a triangle formula: A = 1%2F2b*h
therefore
1%2F2b*(2b+5) = 84
multiply by 2, get rid of the fraction
b(2b+5) = 168
arrange as a quadratic equation
2b^2 + 5b - 168 = 0
you can use the quadratic formula, a=2; b=5; c=-168; but this will factor to
(2b+21)(b-8) = 0
positive solution is all we want here
b = 8 inches is the base
therefore
2(8) + 5 = 21 inches is the height