Let X and Y belong to R, x ^ 2 + 2Y ^ 2 = 6, then the minimum value of X + y is
Let s = x + y, then y = s-x, substituting x ^ 2 + 2Y ^ 2 = 6
x^2+2(S-x)^2=6
3x^2-4Sx+2S^2-6=0
Discriminant = (4S) ^ 2-4 * 3 * (2S ^ 2-6) = - 8s ^ 2 + 72 > = 0
S^2
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