18. 0.0011
20. 1/625
19. 0.0011
21. 1/27
For the limit to exist, the limits from either side must also exist and be identical. We have


Since the limits do not match, the overall limit does not exist.
Answer:
Step-by-step explanation:
an equation is : y = 10x+b
calculate b : this line passes by : (7;1) when x =7 y = 1
so : 10(7)+ b=1
b= -69
so : y = 10x-69