Question

Katrina buys a 42-ft roll of fencing to make a rectangular play area for her dogs.

Answer 1

Answer:

(a) $l = -w + 21$

(b) Domain: $0$ (See attachment for graph)

(c) $f(w) = -w + 21$

Step-by-step explanation:

Given

$2(l + w) = 42$

$l = length$

$w = width$

Solving (a): A function; l in terms of w

All we need to do is make l the subject in $2(l + w) = 42$

Divide through by 2

$l + w = 21$

Subtract w from both sides

$l + w - w = 21 - w$

$l = 21 - w$

Reorder

$l = -w + 21$

Solving (b): The graph

In (a), we have:

$l = -w + 21$

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 $0$

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To check this

When $w = 1$

$l = -1 + 21$

$l = 20$

$(w,l) = (1,20)$

When $w = 20$

$l = -20 + 21$

$l = 1$

$(w,l)= (20,1)$

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See attachment for graph

Solving (c): Write l as a function $f(w)$

In (a), we have:

$l = -w + 21$

Writing l as a function, we have:

$l = f(w)$

Substitute $f(w)$ for l in $l = -w + 21$

$l = -w + 21$ becomes

$f(w) = -w + 21$