SOLUTION: I need to a step by step solving this equation:0= x^2+15x-1350 , This is from a word problem using quadratic equation solving cost per person.... I know the answer but I do not kno

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Question 240797: I need to a step by step solving this equation:0= x^2+15x-1350 , This is from a word problem using quadratic equation solving cost per person.... I know the answer but I do not know how they got it....help please
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
If you 'see' an easy factorization, you can always use that. But for me, once the factors get that large, I prefer the quadratic equation. here is a solver that does it for you --> http://www.algebra.com/algebra/homework/quadratic/quadratic.solver
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B15x%2B-1350+=+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=%2815%29%5E2-4%2A1%2A-1350=5625.

Discriminant d=5625 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-15%2B-sqrt%28+5625+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%2815%29%2Bsqrt%28+5625+%29%29%2F2%5C1+=+30
x%5B2%5D+=+%28-%2815%29-sqrt%28+5625+%29%29%2F2%5C1+=+-45

Quadratic expression 1x%5E2%2B15x%2B-1350 can be factored:
1x%5E2%2B15x%2B-1350+=+1%28x-30%29%2A%28x--45%29
Again, the answer is: 30, -45. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B15%2Ax%2B-1350+%29