SOLUTION: How do I enter this problem to work it? Use formula x=-b/2a to find the coordinates of the vertex for the parabola defined by the quadratic function f(x)=2x^2+4x-15. Substitute

Question 88766: How do I enter this problem to work it?
Use formula x=-b/2a to find the coordinates of the vertex for the parabola defined by the quadratic function f(x)=2x^2+4x-15. Substitute this value into the f(x) to find the y coordinate of the vertex. Plot two points to the left and right of the vertex. Do the graph of the parabola. HELP!!!
Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
Find the vertex of the parabola defined by:
Compare this with the general form:
...and you can see that: a = 2, b = 4, and c = -15
Now substitute a and b into the formula for the x-coordinate of the vertex:

This is the x-coordinate of the vertex. Substitute this value of x into the given quadratic equation and solve for f(x), this is the same as the y-coordinate.
Evaluate.

The coordinates of the vertex are:
(-1, -17)...and the equation of the line of symmetry is:
The graph looks like this:

To plot two points to the left and to the right of the vertex (line of symmetry), choose four values of x-coordinate, such as:
x = 0
x = -2
x = 1
x = -3
and for each one of these, find the corresponding y-coordinate (f(x)) and these will give you the coordinates of the four points.
I'll do one and you can finish the rest.
Substitute x = -3
Evaluate.

The coordinates of this point are: (-3, -9)
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