SOLUTION: solve 3x2+11x=20

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Question 18714: solve 3x2+11x=20
Answer by Alwayscheerful(414) About Me  (Show Source):
You can put this solution on YOUR website!
Move the 20 over to the left side so it is a quadratic equation.
3x%5E2%2B11x-20=0
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 3x%5E2%2B11x%2B-20+=+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=%2811%29%5E2-4%2A3%2A-20=361.

Discriminant d=361 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-11%2B-sqrt%28+361+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%2811%29%2Bsqrt%28+361+%29%29%2F2%5C3+=+1.33333333333333
x%5B2%5D+=+%28-%2811%29-sqrt%28+361+%29%29%2F2%5C3+=+-5

Quadratic expression 3x%5E2%2B11x%2B-20 can be factored:
3x%5E2%2B11x%2B-20+=+3%28x-1.33333333333333%29%2A%28x--5%29
Again, the answer is: 1.33333333333333, -5. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+3%2Ax%5E2%2B11%2Ax%2B-20+%29

Hope this helps!