Matilde wants to build a wooden planter in the shape of a right triangle for their garden. One side will be formed by an existing bench that is 96 inches long. To fence the other two sides, Matilde wants to use pieces of wood that are each precut to 12 inches, so each of the two undetermined side lengths will need to be in whole number of inches. Use the polynomial identity (x2+y2)2=(x2−y2)2+(2xy)2 to find one of the other possible side lengths, assuming 2xy=96 and that the two undetermined sides are of different lengths. Which of the following values could be one of the side lengths for their wooden planter?(1 point)

Responses

24 inches
24 inches

20 inches
20 inches

80 inches
80 inches

100 inches

1 answer

To solve this problem using the given polynomial identity, we start with the equation \(2xy = 96\). From this, we can find \(xy\):

\[ xy = \frac{96}{2} = 48 \]

According to the polynomial identity \((x^2 + y^2)^2 = (x^2 - y^2)^2 + (2xy)^2\), we will substitute \(2xy\) into it. So, we need to calculate \( (2xy)^2 = 96^2 = 9216 \).

Now, we can denote \(x^2 + y^2\) and \(x^2 - y^2\) in terms of \(m\) and \(n\):

\[ (x^2 + y^2)^2 = m^2 + 9216 \]

With \(xy = 48\) and \(x\) and \(y\) being the lengths of the two sides of the triangle, we can rewrite \(x\) and \(y\) in terms of \(s\) and \(d\) (where \(s\) is the shorter side and \(d\) is the longer side):

\[ x = s, \quad y = d \]

From \(s \cdot d = 48\) and \(x = s\) and \(y = d\), we can find some possible pairs \((s,d)\) such that \(s\) and \(d\) are coprime.

Let’s find pairs \((s, d)\) such that \(s \cdot d = 48\).

The factor pairs of 48 are:

  • (1, 48)
  • (2, 24)
  • (3, 16)
  • (4, 12)
  • (6, 8)

Now, we can find the lengths corresponding to those pairs (keeping in mind that we need integer lengths).
The values of \(s\) and \(d\) must be different lengths, and we also need \(s + d\) to comply with the constraints of a right triangle given \(a^2 + b^2 = c^2\).

Given the side lengths suggested (24 inches, 20 inches, 80 inches, 100 inches), we check which one meets our conditions.

Checking Possible Combinations

  1. If we take 24 inches and 48/24 = 2 => (2, 24)
  2. If we take 20 inches, then \(d = 48/20\) => not an integer.
  3. If we take 80 inches, then \(d = 48/80\) => not an integer.
  4. If we take 100 inches, then \(d = 48/100\) => not an integer.

Conclusion

The only pairs of integer side lengths we could achieve here, keeping the existing constraints, point to 24 inches satisfying our conditions.

So, the length of the two undetermined sides that would work is indeed:

24 inches.