Find the maximum or minimum of the following quadratic function: y = -10x^2 + x - 10.
A. -40
B. -10
C. 10
D. -399/40

Question

Find the maximum or minimum of the following quadratic function: y = -10x^2 + x - 10.
	A.	-40
	B.	-10
	C.	10
	D.	-399/40

mathmale · Answer

Just by looking at the first term of this function, you can tell whether the graph opens UP or DOWN.  Which is it, and why?

anonymous · Answer

It's in the negatives

mathmale · Answer

I don't understand.  Explain again, please.
Next, Would you please use x=-b/(2a) to find the x-coordinate of the vertex of your parabola?  x = ?

anonymous · Answer

i got the the answer its -10

anonymous · Answer

i graphed it.

mathmale · Answer

that's a great way to learn what's happening here! Congrats.  Note that if you had found x=-b/(2a), you'd have gotten x=-(1)/(2*[-10]) = 1/20, and using this x value would give you the corresponding y value.

mathmale · Answer

Note that you still have to say whether you've found a max or a min.