SOLUTION: Solve the following quadratic equations by factoring. x2 + x - 20 = 0 x = 5 x = 4 x = 4 or x = -5 x = -4 or x = 5 4. 2x2 – 15 = –7x

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Question 460074: Solve the following quadratic equations by factoring.
x2 + x - 20 = 0
x = 5
x = 4
x = 4 or x = -5
x = -4 or x = 5
4. 2x2 – 15 = –7x
x = 1.5 or x = -3
x = 1.5 or x = -5
x = 3 or x = -5
x = 1.5 or x = 5

5. 3x2 – 5x = 2
x = 1/3 or x = 3
x = 1/3 or x = 2
x = -1/3 or x = 2
x = - 1/3 or x = 3

6. 3x2 + 3 = 10x
x = 1/3 or x = 3
x = 1/3 or x = 2
x = -1/3 or x = 2
x = - 1/3 or x = 3

7. Solve the following quadratic equations using the quadratic formula.
x2 + 7x + 9 = 0





8. x2 + 6x = 0
x = 1 or x = 6
x = 0 or x = 6
x = 0 or x = -6


9. 15x2 – 7x – 2 = 0
x = 2/3 or x = -1/5
x = -2/3 or x = 1/5
x = 3/2 or x = -5
x = -3/2 or x = 5

10. x2 - 9x + 5 = 0





Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
9. 15x2 – 7x – 2 = 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 15x%5E2%2B-7x%2B-2+=+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=%28-7%29%5E2-4%2A15%2A-2=169.

Discriminant d=169 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--7%2B-sqrt%28+169+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-7%29%2Bsqrt%28+169+%29%29%2F2%5C15+=+0.666666666666667
x%5B2%5D+=+%28-%28-7%29-sqrt%28+169+%29%29%2F2%5C15+=+-0.2

Quadratic expression 15x%5E2%2B-7x%2B-2 can be factored:
15x%5E2%2B-7x%2B-2+=+%28x-0.666666666666667%29%2A%28x--0.2%29
Again, the answer is: 0.666666666666667, -0.2. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+15%2Ax%5E2%2B-7%2Ax%2B-2+%29

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Ignore the incorrect factoring by the solver.
x = -1/5
x = 2/3
Do the others the same way.