Is x^2-x-2 concave up or down?

Question

anonymous · Answer

According to my notes, if f'(x) or f''(x)>0, it should be concave up and <0 concave down. Are my notes wrong?

anonymous · Answer

to see if something is concave up or down you should be looking for the second derivative and see whether it is negative or positive, so yeah your notes are correct.

anonymous · Answer

It's negative. Does that mean that the original fxn is concave down in the entire domain?

anonymous · Answer

you really need no calc for this
it is a parabola that opens up

anonymous · Answer

I know that. It's pretty obvious but I want to understand how to do it with calc.

anonymous · Answer

the second derivative is a constant 
if the

anonymous · Answer

$$y=ax^2+ bx+c$$
$$y'=2ax+b\
y''=2a$$it depends entirely on the sign of the leading coefficient, just like you know

anonymous · Answer

Oh darn. I'm stupid. calculation mistake