You can think of it this way, if x is less than -3, for example, x gets -4. Then the square of x is equal to 16, greater than 9, which does not meet the problem condition; For example, if x is greater than 3, then x equals 4. Then the square of x is also equal to 16, which is greater than 9. Therefore, the value of x is between -3 and 3. You can also take the value of x equal to 2 to verify.