Determine whether the graph of y = −3x2 + 2x − 8 opens up or down and whether it has a maximum or minimum point.

Question

anonymous · Answer

I think it's  Down; Minimum?

anonymous · Answer

The graph is pointing down, and it has a MAXIMUM point. An upside-down parabola does not have a minimum because it stretches infinitely downward. However, it does have a maximum, which is its peak since it is upside down.

anonymous · Answer

what about "Determine whether the graph of y = x2 + 2x − 8 has a maximum or minimum point, then find the maximum or minimum value."

anonymous · Answer

Maximum; (-9, -1)?

anonymous · Answer

Lemme do it real quick.

anonymous · Answer

Do you have the formula for min and max or are you using derivatives?

anonymous · Answer

I don't know the formula

anonymous · Answer

Okay, I know how to figure this out. Here, I'll show you.

anonymous · Answer

f(-b/2a)

Therefore, you need to plug in -(2)/(2)(1). This equals -1. That is your x-coordinate for the vertex of the parabola, which is its MINIMUM point. To find y, you need to plug in (-1) into the original equation. Like so, 

(-1)^2 + 2(-1) - 8 = -11. Therefore, the minimum point is (-1, -11)