Answer:
B
Step-by-step explanation:
Rocco: of the job per hour
Giulia: of the job per hour
Together: of the job per hour
Rocco + Giulia = Together


3x + 21 = 7x
21 = 4x

It will take Giulia
hours to paint the room by herself.
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Giulia:
B)


1=1
so it's true
Answer:
The change in delta x would be 0 in the second option because the change is exactly the same.
I'll use subscript notation for brevity, i.e.
.
By the chain rule,



We have

and

When
, we have

and the partial derivatives take on values of

So we end up with
