How to find the number of zeros of a function Be specific

How to find the number of zeros of a function Be specific

In fact, the most practical way is to use the monotonicity of function to divide the interval of definition domain. After obtaining the maximum or minimum value of each interval and comparing with 0, we can determine whether there is zero point in each interval. This method is the most practical and not easy to miss the number. Secondly, it is the combination of number and shape, combined with the special properties of some functions