SOLUTION: The length of a rectangle is 7 centimeters less than four times its width. Its area is 15 square centimeters. Find the dimensions of the retangle. Width = Length=

Question 344479: The length of a rectangle is 7 centimeters less than four times its width. Its area is 15 square centimeters. Find the dimensions of the retangle.
Width =
Length=
Answer by JBarnum(2146) (Show Source): You can put this solution on YOUR website!
a=lw
a=15
l=4w-7
15=4w^2-7w
0=4w^2-7w-15
w=3 since it cant be negative
l=5

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=289 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 3, -1.25. Here's your graph:

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