SOLUTION: Solve by using quadratic formula: (r-4)(r+12)=16

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Question 594223: Solve by using quadratic formula:
(r-4)(r+12)=16
Found 2 solutions by rfer, Alan3354:
Answer by rfer(16322) About Me  (Show Source):
You can put this solution on YOUR website!
r^2+12r-4r-48=16
y=-r^2-8r+64
(5,0)
(-13,0)
y int (0,64)
opens down

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by using quadratic formula:
(r-4)(r+12)=16
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r%5E2+%2B+8r+-+48+=+16
r%5E2+%2B+8r+-+64+=+0
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Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B8x%2B-64+=+0) has the following solutons:

x%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=%288%29%5E2-4%2A1%2A-64=320.

Discriminant d=320 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-8%2B-sqrt%28+320+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%288%29%2Bsqrt%28+320+%29%29%2F2%5C1+=+4.94427190999916
x%5B2%5D+=+%28-%288%29-sqrt%28+320+%29%29%2F2%5C1+=+-12.9442719099992

Quadratic expression 1x%5E2%2B8x%2B-64 can be factored:
1x%5E2%2B8x%2B-64+=+%28x-4.94427190999916%29%2A%28x--12.9442719099992%29
Again, the answer is: 4.94427190999916, -12.9442719099992. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B8%2Ax%2B-64+%29

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