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.

## some questions from GR 0568

### 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.

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.