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Explanation:
Apply the difference of squares rule
x^2 - y^2 = (x-y)(x+y)
x^2 - y^2 = (5)(1)
x^2 - y^2 = 5
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Alternatively, you can solve the system
[tex]\begin{cases}x-y=5\\x+y = 1\end{cases}[/tex]
for x and y to get (x,y) = (3,-2).
Then compute x^2-y^2 = 3^2-(-2)^2 = 9-4 = 5
