The value of c for which the considered trinomial becomes perfect square trinomial is: 20 or -20
<h3>What are perfect squares trinomials?</h3>
They are those expressions which are found by squaring binomial expressions.
Since the given trinomials are with degree 2, thus, if they are perfect square, the binomial which was used to make them must be linear.
Let the binomial term was ax + b(a linear expression is always writable in this form where a and b are constants and m is a variable), then we will obtain:

Comparing this expression with the expression we're provided with:

we see that:

Thus, the value of c for which the considered trinomial becomes perfect square trinomial is: 20 or -20
Learn more about perfect square trinomials here:
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Part A
<h3>Answer:
h^2 + 4h</h3>
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Explanation:
We multiply the length and height to get the area
area = (length)*(height)
area = (h+4)*(h)
area = h(h+4)
area = h^2 + 4h .... apply the distributive property
The units for the area are in square inches.
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Part B
<h3>Answer:
h^2 + 16h + 60</h3>
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Explanation:
If we add a 3 inch frame along the border, then we're adding two copies of 3 inches along the bottom side. The h+4 along the bottom updates to h+4+3+3 = h+10 along the bottom.
Similarly, along the vertical side we'd have the h go to h+3+3 = h+6
The old rectangle that was h by h+4 is now h+6 by h+10
Multiply these expressions to find the area
area = length*width
area = (h+6)(h+10)
area = x(h+10) ..... replace h+6 with x
area = xh + 10x .... distribute
area = h( x ) + 10( x )
area = h( h+6 ) + 10( h+6 ) .... plug in x = h+6
area = h^2+6h + 10h+60 .... distribute again twice more
area = h^2 + 16h + 60
You can also use the box method or the FOIL rule as alternative routes to find the area.
The units for the area are in square inches.
The amount each friend does pay is £9.75
<h3>How to calculate the pay of each friend using fractions and arithmetic operations?</h3>
We are going to find 5% of the total amount paid and divide it by the numbers of all the friends to determine the amount paid by each one of them.
From the given information:
- The 5% of 130 = £6.5
- Total amount paid = £130 + £6.5 = £136.5
Therefore, the cost of each friend is = 
The cost of each friend = £9.75
Learn more about fractions here:
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After every month's withdrawals, 4/5 of the original amount at the start of the month will remain. The amount at the start of every month will change. Thus:
an = 4/5 (an-1) ; where a1 = 500.