If \( x^{2}+y^{2}=80 \) and \( x y=12 \), find the value of \( (x-y)^{2} \)
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To find the value of \( (x-y)^{2} \), we start with the identity: \[ (x-y)^{2} = (x+y)^{2} - 4xy \] We need to calculate \( x+y \) and \( xy \). We are given that \( xy = 12 \) directly. Next, we can find \( x+y \) using the equation \( x^{2} + y^{2} = 80 \). Using the identity: \[ x^{2} + y^{2} = (x+y)^{2} - 2xy \] We can substitute \( xy = 12 \): \[ 80 = (x+y)^{2} - 2(12) \] This simplifies to: \[ 80 = (x+y)^{2} - 24 \] So, adding 24 to both sides gives: \[ (x+y)^{2} = 80 + 24 = 104 \] Now we have both \( (x+y)^{2} \) and \( xy \): \[ (x-y)^{2} = (x+y)^{2} - 4xy = 104 - 4(12) \] Calculating \( 4(12) \): \[ 4(12) = 48 \] Thus, \[ (x-y)^{2} = 104 - 48 = 56 \] Therefore, the value of \( (x-y)^{2} \) is \[ \boxed{56} \]