Find the coordinate of the vertex.
There are many ways to find a vertex. One way is by using the formula:
This will give you the x-value of the vertex. Then evaluate y = 2x2 + 6x − 20 to find the y-coordinate.
Find the equation of the line in point-slope form.
Since the slope is given and a point is known (the vertex), find the equation of the line in point-slope form: y − y1 = m(x − x1)