1 domain. F(x) is r, which means that whatever value the function f(x) takes is meaningful, that is, mx? +MX+ 1 & gt； The 0 constant holds, which is discussed in different situations:

(1) When m

② When m=0 and y= 1, then y is always positive, regardless of the value of x, and f(x) is always meaningful.

③ When m >; 0, so that the y constant is greater than 0, then δ ≦ 0, that is, m? -4m≦0, and you get 0≦m≦4, because m>0, so 0.

To sum up, we can get 0≦m≦4.

2. Let y=x+ 1/x- 1.

Then let 1

y2-y 1

= x2+ 1/x2- 1-(x 1+ 1/x 1- 1)

=(x2-x 1)+( 1/x2- 1/x 1)

=(x2-x 1)+(x 1-x2)/x 1x 2

=(x2-x 1)( 1- 1/x 1x 2)

Because x2>x1>; 1, so x2-x1>; 0，x 1x 2 & gt； 1，0 & lt； 1/x 1x 2 & lt； 1，0 & lt； 1- 1/x 1x 2 & lt； 1

So y2-y 1 >: 0

So y=x+ 1/x- 1 is the increasing function at (1, +∞).

So when 0

When a> is at 1, f(x) is increasing function.