Find the instantaneous rate of change at $ x=1$

Question

As I have said on my previous question ,I have a quiz tomorrow! And I need to get ready , but this question in my quiz review has been a problem for me! So basically it asks the instantaneous rate of change when $x=1$.

4A Is preety easy on the above questions , but 4B Has been hunting me!

Find the instantaneous rate of change at x=1.

4C , and 4D Are the same types of question as they both ask the slope of the line , so all you have to do is find the points from (2,2.5) (for 4C) , then you get the slope using $\frac{y_2-y_1}{x_2-x_1}$

Answer from teacher I couldn't understand:

Answer 1

At $x=1$, draw a tanget line. The slope of that tanget line will give you the instantaneous rate of change at $x=1$. The tanget line has slope $m=0$.

Answer 2

Before 1 second the rate of change is positive because the line is going up. After 1 second the rate of change is negative because the line is going down.

At 1 second the line is flat so it must be zero.