   SEARCH HOME Math Central Quandaries & Queries  Subject: Dimensions of a rectangle Name: Harold Who are you: Other L=3w-4 A=96Square I used the quadratic equation to solve and my answer is still wrong I convert the square of 1168 to decimal. here is where i start (3w-4) x w=96 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.>     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.