You can directly substitute 9 into the expression of X =(3-3)/(8 1-9)=0.

2. this kind of topic is the maximum degree term in which the numerator and denominator are divided by x at the same time. in this topic, the numerator and denominator are divided by x 3 at the same time.

(x^2+2x-3)/(x^3-2*x^2-6)=( 1/x+2/x^2-3/x^3)( 1-2/x-6/x^3)

In this way, you can clearly see that when x approaches positive infinity, 1/x 2/x 23/x 3 all tend to 0, that is, the numerator tends to 0, while the denominator tends to 1.

So the formula =0

3. When x approaches 0, there is sinX/X tending to 1.

(sin5X)/(sin6X)= 5/6 *(sin5X/5X)/(sin6X/6X)= 5/6

4. As soon as you look at the numerator and denominator, you can know that this topic can be simplified first, omitting the items that may tend to 0, and then directly substituting A into the expression of X.

(x^3-a^3)/(x-a)=(x-a)(x^2+ax+a^2)/(x-a)

=X^2+AX+A^2

Substitute a into X.

The above formula = 3a 2

I hope it will help you, hope to adopt it, thank you ~ ~