That is, m ≥-[x 2+1]/x =-(x+1/x)

That is, m≥[-(x+ 1/x)]max.

And x+ 1/x≥2√x× 1/x=2, and x= 1.

So the minimum value of x+ 1/x is 2.

That is [-(x+ 1/x)]max=-2.

M≥-2

So choose a.