Use the polynomial identity [tex]\left(x^2 + y^2\right)^2 = \left(x^2 - y^2\right)^2 + (2xy)^2[/tex] to find a Pythagorean triple when [tex]x = 9[/tex] and [tex]y = 4[/tex].

A. 65, 72, 113
B. 16, 81, 97
C. 36, 45, 97
D. 65, 72, 97



Answer :

To solve this problem, we will use the given polynomial identity step-by-step to find the correct Pythagorean triple when [tex]\( x = 9 \)[/tex] and [tex]\( y = 4 \)[/tex].

The polynomial identity given is:
[tex]\[ (x^2 + y^2)^2 = (x^2 - y^2)^2 + (2xy)^2 \][/tex]

First, let's calculate each term separately using [tex]\( x = 9 \)[/tex] and [tex]\( y = 4 \)[/tex].

1. Calculate [tex]\( (x^2 + y^2)^2 \)[/tex]
[tex]\[ x^2 + y^2 = 9^2 + 4^2 = 81 + 16 = 97 \][/tex]
[tex]\[ (x^2 + y^2)^2 = 97^2 = 9409 \][/tex]

2. Calculate [tex]\( (x^2 - y^2)^2 \)[/tex]
[tex]\[ x^2 - y^2 = 9^2 - 4^2 = 81 - 16 = 65 \][/tex]
[tex]\[ (x^2 - y^2)^2 = 65^2 = 4225 \][/tex]

3. Calculate [tex]\( (2xy)^2 \)[/tex]
[tex]\[ 2xy = 2 \cdot 9 \cdot 4 = 72 \][/tex]
[tex]\[ (2xy)^2 = 72^2 = 5184 \][/tex]

We now have the following terms:
[tex]\[ (x^2 + y^2)^2 = 9409 \][/tex]
[tex]\[ (x^2 - y^2)^2 = 4225 \][/tex]
[tex]\[ (2xy)^2 = 5184 \][/tex]

Checking the provided options, we compare our calculated values:
- Option a) [tex]\( 65, 72, 113 \)[/tex] does not match any of the terms.
- Option b) [tex]\( 16, 81, 97 \)[/tex] does not match.
- Option c) [tex]\( 36, 45, 97 \)[/tex] does not match.
- Option d) [tex]\( 65, 72, 97 \)[/tex] matches exactly with the given terms.

Hence, the correct Pythagorean triple when [tex]\( x = 9 \)[/tex] and [tex]\( y = 4 \)[/tex] is:
[tex]\[ \boxed{d) \ 65, 72, 97} \][/tex]