How do you graph y equals x2 2x 8?

Answer 1

y = x2 + 2x + 8

a = 1 > 0 the parabola opens upward, b = 2, c = 8 the y-intercept is (0, 8).

axis of symmetry: x = -b/2a = -1

The axis of symmetry passes through x = -1, so we have the point (-2, 8) which is symmetrical to (0, 8).

Let f(x) = y, and evaluate f(-1) to find the y-coordinate of the vertex.

f(-1) = (-1)2 + 2(-1) + 8 = 7; vertex = (-1, 7).

Since the parabola opens upward and the vertex lies on the second quadrant, there are no x-intercepts.

Evaluate f(1) = (1)2 + 2(1) + 8 = 11; (1, 11) symmetrical to (-3, 11).

Just plot the points and draw the parabola.