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| Math Central | Quandaries & Queries |
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Subject: Dimensions of a rectangle L=3w-4 I convert the square of 1168 to decimal. here is where i start could you give me an example |
Hi Harold.
The quadratic equation should indeed give you the right answer.
You've set up the problem correctly as well.
(3w-4) x w=96
3w2 -4w - 96 = 0
let a = 3, b = -4, c = -96
then
w = (-b +/- sqrt(b2-4ac) ] / (2a)
w = (4 +/- sqrt(16-4(3)(-96)) ] / (2(3))
w = (4 +/- sqrt(1168) ] / 6
w = (4 +/- 34.18) / 6
w = 38.18 / 6
w = 6.36
To verify, let's plug it into the original equations:
w = 6.36
l = (3w - 4) = (3(6.36) - 4) = 15.08
A = wl = 6.36(15.08) = 96 (with rounding)
This is the correct answer. If your calculator tells you differently, change the batteries. If your textbook tells you differently, plug their value in for w and calculate A - you will find it must be a mistake in the book.
Stephen La Rocque.>
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