How do i use the quadratic formula in this situation
asked Dec 7, 2016 in Algebra 2 Answers by anonymous

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1 Answer

If L and W are length and width, L=3W-9, WL=5760.

So W(3W-9)=5760; 3W^2-9W-5760=0; W^2-3W-1920=0.

Completing the square: W^2-3W+9/4=1920+9/4; (W-3/2)^2=√1922.25, W-3/2=43.8435 approx.

Therefore W=45.3435 feet and L=127.0304 feet (approx).

Using the quadratic formula W=(3+√(9+7680))/2=45.3435' (the same result as completing the square).

Perimeter=2(L+W)=344.75' approx.

answered Dec 8, 2016 by Rod Top Rated User (487,420 points)
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