-4, 4, 1/2, -1/2
Work Step by Step
$4x^4-65x^2+16 = 4x^4-64x^2 - x^2+16 = 4x^2(x^2-16) - 1(x^2-16) = (4x^2-1)(x^2-16)=0$ Either $4x^2-1 = (2x-1)(2x+1) = 0 $ giving x = 1/2 or -1/2 or $x^2-16 = (x-4)(x+4) = 0$ giving x=4 or -4
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