| x^2(x^2 +1)^(-(n+2)/2) = x^2(x^2 +1)^(-(n+2)/2) + {(x^2 +1)^(-(n+2)/2) - (x^2 +1)^(-(n+2)/2)} = {x^2(x^2 +1)^(-(n+2)/2) + (x^2 +1)^(-(n+2)/2)} - (x^2 +1)^(-(n+2)/2) = (x^2 +1)(x^2 +1)^(-(n+2)/2) - (x^2 +1)^(-(n+2)/2) = (x^2 +1)^1 × (x^2 +1)^(-(n+2)/2) - (x^2 +1)^(-(n+2)/2) = (x^2 +1)^{1 + (-(n+2)/2)} - (x^2 +1)^(-(n+2)/2) = (x^2 +1)^(-n/2) - (x^2 +1)^(-(n+2)/2)
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