SOLUTION: A flat panel monitor are such that its length is 3 in. more than its width. If length were doubled and if the width were decreased by 1 in., the area would be increased by 150 in.2

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Question 167152: A flat panel monitor are such that its length is 3 in. more than its width. If length were doubled and if the width were decreased by 1 in., the area would be increased by 150 in.2(squared). What are the length and width of flat panel monitor?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
A flat panel monitor are such that its length is 3 in. more than its width. If length were doubled and if the width were decreased by 1 in., the area would be increased by 150 in.2(squared). What are the length and width of flat panel monitor?
.
Let w = width of monitor
then
w+3 = length of monitor
.
double length = 2(w+3)
width decreased by 1 = w-1
.
2(w+3)(w-1) =150
2(w^2-w+3w-3) =150
2(w^2+2w-3) =150
w^2+2w-3 =75
w^2+2w-78 = 0
.
Using the quadratic equation to solve, we find the roots as:
w = {7.888, -9.888}
.
We can toss out the negative solution since it doesn't make sense.
w = 7.888 inches (width)
.
length:
w+3 = 7.888+3 = 10.888 inches (length)
.
Details of quadratic:
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation aw%5E2%2Bbw%2Bc=0 (in our case 1w%5E2%2B2w%2B-78+=+0) has the following solutons:

w%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%282%29%5E2-4%2A1%2A-78=316.

Discriminant d=316 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-2%2B-sqrt%28+316+%29%29%2F2%5Ca.

w%5B1%5D+=+%28-%282%29%2Bsqrt%28+316+%29%29%2F2%5C1+=+7.88819441731559
w%5B2%5D+=+%28-%282%29-sqrt%28+316+%29%29%2F2%5C1+=+-9.88819441731559

Quadratic expression 1w%5E2%2B2w%2B-78 can be factored:
1w%5E2%2B2w%2B-78+=+1%28w-7.88819441731559%29%2A%28w--9.88819441731559%29
Again, the answer is: 7.88819441731559, -9.88819441731559. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B2%2Ax%2B-78+%29