Answer:
(a) 
(b) Domain:
<em>(See attachment for graph)</em>
(c) 
Step-by-step explanation:
Given



Solving (a): A function; l in terms of w
All we need to do is make l the subject in 
Divide through by 2

Subtract w from both sides


Reorder

Solving (b): The graph
In (a), we have:

Since l and w are the dimensions of the fence, they can't be less than 1
So, the domain of the function can be 
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To check this
When 



When 


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<em>See attachment for graph</em>
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Solving (c): Write l as a function 
In (a), we have:

Writing l as a function, we have:

Substitute
for l in 
becomes

Answer:
The second one is correct.
Answer:
y=4x-5.
Step-by-step explanation:
slop-interception form of the required line is y=kx+b, where k - slop, b - intercept;
1) to find value of k:
if the required line is parallel to the given line, then slop of the given line = slop of the required line, it means k=4 and the required line is y=4x+b;
2) to find the value of 'b':
if to substitute the given coordinates into the equation of the given line, then:
15=4*5+b, b= -5.
3) finally, y=4x-5