Below, replace the root with () 0.5 and the square with () 2.

The first question: firstly, M>0, N>0;

Secondly, m2-N2 = (a+1+a-2 * (a * (a+1)) 0.5)-(a+1+a-2 * (a * (a-1)).

= 2 * (a * (a-1)) 0.5-2 * (a * (a+1)) 0.5, which is obviously less than zero, so m < N；;

Second question: 2 * a 2+3-4 * a = (2 * a 2-4a+2)+1= 2 * (a-1) 2+1> 0.

So it should be 2a 2+3 >；; 4a