SOLUTION: Please help with the following problem. Consider the function f(x)=x^2+6x-2. Find h, the x-coordinate of the vertex of this parabola.

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: Please help with the following problem. Consider the function f(x)=x^2+6x-2. Find h, the x-coordinate of the vertex of this parabola.      Log On


   



Question 164879: Please help with the following problem. Consider the function f(x)=x^2+6x-2. Find h, the x-coordinate of the vertex of this parabola.
Found 2 solutions by jim_thompson5910, KnightOwlTutor:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
For any quadratic y=ax%5E2%2Bbx%2Bc, the x-coordinate of the vertex can be found by the formula


x=%28-b%29%2F%282a%29


From f%28x%29=x%5E2%2B6x-2 we can see that a=1, b=6 and c=-2


x=%28-6%29%2F%282%281%29%29 Plug in a=1 and b=6


x=%28-6%29%2F%282%29 Multiply


x=-3 Reduce


So the x-coordinate of the vertex is x=-3

Answer by KnightOwlTutor(293) About Me  (Show Source):
You can put this solution on YOUR website!
You first have to complete the square.
0=x^2+6x-2
Add 2 to both sides
2=x^2+6x
Take the 6 and half it. Then take the value in this case it is 3 and square it.add 9 to both sides.
2+9=(x+3)^2
0=(x+3)^2-11
The vertex is at (3,-11)
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B6x%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=%286%29%5E2-4%2A1%2A-2=44.

Discriminant d=44 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-6%2B-sqrt%28+44+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%286%29%2Bsqrt%28+44+%29%29%2F2%5C1+=+0.3166247903554
x%5B2%5D+=+%28-%286%29-sqrt%28+44+%29%29%2F2%5C1+=+-6.3166247903554

Quadratic expression 1x%5E2%2B6x%2B-2 can be factored:
1x%5E2%2B6x%2B-2+=+1%28x-0.3166247903554%29%2A%28x--6.3166247903554%29
Again, the answer is: 0.3166247903554, -6.3166247903554. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B6%2Ax%2B-2+%29