a, 6/x^2-1+5=8x-1/4x+4-12x-1/4-4x b, 1/x+3+8/(x+1)(x-3)=x+3/x^2-2x-3 c, 6x+5/12x+9+3x-7/9-12x=4x^2+10x-7/16x^2-9

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