SOLUTION: Solving a word promblem using a quadratic equation with rational roots The length of a rectangle is 1 yd less than three times ite width and the area of the rectangle is 24yd^2.

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Question 91488: Solving a word promblem using a quadratic equation with rational roots
The length of a rectangle is 1 yd less than three times ite width and the area of the rectangle is 24yd^2. Find the diminsions.

Found 2 solutions by ptaylor, Earlsdon:
Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!
Area of a rectangle=Length times Width or A=L*W
Let W=width of the rectangle
Then Length (L)=3W-1
And Area= 24 yd^2 =W*(3W-1)=3W^2-W So our equation to solve is:
3W^2-W=24 subtract 24 from both sides
3W^2-W-24=24-24 simplifying, we get:
3W^2-W-24=0 quadratic in standard form. We'll solve using the quadratic formula
W+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
W=+%28%2B1+%2B-+sqrt%28+1%5E2%2B4%2A3%2A24+%29%29%2F%282%2A3%29+
W+=+%28%2B1+%2B-+sqrt%28+289+%29%29%2F%286%29+
W=+%28%28%2B1+%2B-+17+%29%2F%286%29%29+
W=+%28%28%2B1+%2B17+%29%2F%286%29%29+ and
W=+%28%28%2B1+-+17+%29%2F%286%29%29+ discount negative value for W
W=+%28%2818+%29%2F%286%29%29+
W=3 yds--------------------------------width
L=3W-1=3%2A3-1=8 yds ---------------------------length
CK
A=24=3*8
24=24

Hope this helps---ptaylor


Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let W = the width of the rectangle and L = the length.
The problem description tells you that the length, L, is (=) 1 yd less than three times its width (L = 3W-1).
You also know that the area, A = 24 sq.yds.
Starting with the formula for the area of a rectangle: A = L*W
Making the appropriate substitutions into the formula, you get:
%283W-1%29%28w%29+=+24 Simplifying this:
3W%5E2-W+=+24 Subtract 24 from both sides.
3W%5E2-W-24+=+0 You can solve this quadratic equation by factoring.
%283w%2B8%29%28W-3%29+=+0 Apply the zero products principle:
3W%2B8+=+0 or W-3+=+0, so...
3W%2B8+=+0 Subtract 8 from both sides.
3W+=+-8 Divide both sides by 3.
W+=+-8%2F3 Discard this solution a negative width is not meaningful.
W-3+=+0 Add 3 to both sides.
W+=+3 The width is 3 yards.
L+=+3W-1
L+=+3%283%29-1
L+=+9-1
L+=+8 The length is 8 yards.
Check:
A+=+L%2AW
A+=+8%283%29
A+=+24sq.yds.