1. **Problem statement:**
We have a rectangular prism with length $p$ cm, width and height each $2$ cm less than the length, i.e., width = height = $p-2$ cm.
2. **Part a) Surface area expression:**
Surface area (SA) of a rectangular prism is given by:
$$SA = 2(lw + lh + wh)$$
where $l = p$, $w = p-2$, and $h = p-2$.
3. **Calculate each term:**
$$lw = p(p-2) = p^2 - 2p$$
$$lh = p(p-2) = p^2 - 2p$$
$$wh = (p-2)(p-2) = (p-2)^2 = p^2 - 4p + 4$$
4. **Sum inside the parentheses:**
$$lw + lh + wh = (p^2 - 2p) + (p^2 - 2p) + (p^2 - 4p + 4) = 3p^2 - 8p + 4$$
5. **Surface area:**
$$SA = 2(3p^2 - 8p + 4) = 6p^2 - 16p + 8$$
6. **Factor the surface area expression:**
Factor out 2:
$$SA = 2(3p^2 - 8p + 4)$$
Try factoring the quadratic inside:
$$3p^2 - 8p + 4 = (3p - 2)(p - 2)$$
7. **Final factored form:**
$$SA = 2(3p - 2)(p - 2)$$
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8. **Part b) Total length of edges of two square faces:**
The two square faces are the ones with sides $p-2$ (width and height).
Each square has 4 edges of length $p-2$, so two squares have:
$$2 imes 4 imes (p-2) = 8(p-2)$$
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9. **Part c) Given ratio and find volume:**
The ratio of surface area to total edge length of the two squares is $10:1$:
$$\frac{SA}{8(p-2)} = 10$$
Substitute $SA$ from part a):
$$\frac{2(3p - 2)(p - 2)}{8(p-2)} = 10$$
Simplify numerator and denominator:
$$\frac{2(3p - 2)(p - 2)}{8(p-2)} = \frac{2(3p - 2)}{8} = \frac{3p - 2}{4}$$
Set equal to 10:
$$\frac{3p - 2}{4} = 10$$
Multiply both sides by 4:
$$3p - 2 = 40$$
Add 2:
$$3p = 42$$
Divide by 3:
$$p = 14$$
10. **Calculate volume:**
Volume $V = l imes w imes h = p imes (p-2) imes (p-2)$
Substitute $p=14$:
$$V = 14 imes 12 imes 12 = 2016$$
**Final answer:**
- Surface area: $$SA = 2(3p - 2)(p - 2)$$
- Total length of edges of two square faces: $$8(p-2)$$
- Volume when ratio is 10:1: $$2016$$ cubic cm
Rectangular Prism B7F21A
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