## some questions from GR 0568

Forum for the GRE subject test in mathematics.
sandraizbasa
Posts: 8
Joined: Tue Jul 14, 2009 5:24 am

### some questions from GR 0568

These are what I am not sure:

14 22 28 31 36 38 39 46 49 52 54 55 60 61 62 65

Any replies will be greatly appreciated.If some of them have been answered before, just skip them.

yoyobarn
Posts: 80
Joined: Sun Dec 19, 2010 7:01 am

### Re: some questions from GR 0568

For Q31,
we can note that $$y'=1+y^4>0$$, and $$y''=4y^3\cdot y'$$. Hence, the graph should be increasing everywhere, and concave when y<0, and convex when y>0.

I think the above is enough to pick option (A).

Furthermore, at y=0, y'=1, and (A) also fits that.