GRE
The radius of $$C_1$$
Twice the radius of $$C_2$$
The standard deviation of the seven numbers $$-c, -b, -a, 0, a, b, c$$
The standard deviation of the seven numbers $$-c^{2}, -b^{2}, -a^{2}, 0, a^{2}, b^{2}, c^{2}$$
x
y
$$d$$
$$k^2$$
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