On graph paper, use a table to make a complete graph of y = x2 − 2x − 8. Homework Help ✎

Question

Write the coordinates of the y-intercept. What is the connection between the y‑intercept and the equation y = x2 − 2x − 8?
Write the coordinates of the x-intercepts.
What is the lowest point on the graph?

Answer 1

Of course, it is not possible to make a "complete" graph of a parabola on finite graph paper.

If y = x^2-2x-8 then clearly the y-intercept is -8, since that's what you get when x=0

x^2-2x-8 = (x-1)^2 - 9

So the vertex is at (1,-9), which is the lowest point on the graph.

For the x-intercepts, y=0, so

x-1 = ±3, so x = -2 or 4