Tìm x: a) x^2 - 3x - 10 = 0; b) x^2 + 7x = -12; c) (2x - 1)^2 - (4x^2 - 1) = 0

a) x^2-3x-10=0
b) x^2 +7x=-12
c) (2x-1)^2-(4x^2-1)=0
d) x^2(x^2+4)-x^2-4=0
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