Step 1: Determine the domain of y=f(x).

Step 2: Find the derivative of f'(x) and the root of f'(x)=0.

Step 3: The undefined point of the function and the root of f'(x)=0 divide the domain of f(x) into several intervals, and discuss the monotonicity of the function in several intervals respectively.

Emergence method 4: in the interval, if f' (x) >; 0, the function monotonically increases in this interval, and if f' (x)

Second, the definition method

1, the definition method is monotonically increasing.

If the values of any two independent variables on the interval d in the definition domain are both x 1, x2, when X 1

2. The definition method is monotonously decreasing.

When x 1, if is subtracted from the value of any two independent variables in the interval d of the domain X 1, x2.