For what values of k does the equation 2x^2-kx+8=0 have a repeated root?
The quadratic ax^2 + bx + c = 0 has repeated roots when b^2 - 4ac = 0, so
(-k)^2 - 4*2*8 = 0 gives k^2 = 64 or k = +8 and k = -8
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