Y=4x+9 is not a direct variation an example of a direct variation is y=2x
The formula of a slope:

We have:

Substitute

Answer: The slope is not defined.
Answer:
4x+4y=1, 6x-y=1
x+y=4, x-y=2
x-y=9, x+y=6
Step-by-step explanation:
Answer: a
Step-by-step explanation: edge 2020
(2,4) is the interval minimum for 0