Answer:
Step-by-step explanation:
Expression for the rectangular area and perimeter are, respectively:
After some algebraic manipulation, area expression can be reduce to an one-variable form:
The first derivative of the previous equation is:
Let the expression be equalized to zero:
The second derivative is:
According to the Second Derivative Test, the critical value found in previous steps is a maximum. Then:
The maximum area is:
Let's replace x with -4 and simplify
y = (x/4) + 7
y = (-4/4) + 7
y = -1 + 7
y = 6
This means x = -4 and y = 6 pair up together.
So 6 goes in the box under the -4
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Repeat those steps for x = 0
y = (x/4) + 7
y = (0/4) + 7
y = 0 + 7
y = 7
So 7 goes in the box under the 0
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Let's repeat those steps for x = 4
y = (x/4) + 7
y = (4/4) + 7
y = 1 + 7
y = 8
So 8 goes in the box under the 4
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Lastly, for x = 8, we get
y = (x/4) + 7
y = (8/4) + 7
y = 2 + 7
y = 9
9 goes in the box under the 8
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The y outputs we got were: 6, 7, 8, 9
Notice how each time y increases by 1, x goes up by 4.
This means slope = rise/run = 1/4
We can think of x/4 as (1/4)x to help see that the slope is 1/4.
