①x+2÷x=3x²+2=3xx²-3x+2=0(x-1)(x-2)=0x=1或x=2②x+6÷x=5x²+6=5xx²-x+5=0(x-1)(x-5)=0x=1或x=5③x+12÷x=7x²+12=7xx²-7x+12=0(x-3)(x-4)=0x=3或x=4x+(n²+n)÷(x-3)=2n+4x(x-3...正确的解答应该是：①x+2÷x=3 x²+2=3xx²-3x+2=0(x-1)(x-2)=0x=1或x=2②x+6÷x=5x²+6=5xx²-5x+6=0(x-2)(x-3)=0x=2或x=3 ③x+12÷x=7x²+12=7xx²-7x+12=0(x-3)(x-4)=0x=3或x=4 则x+(n²+n)÷(x-3)=2n+4(x-3)+(n²+n)÷(x-3)+3=2n+4(x-3)+n(n+1)÷(x-3)=2n+1(x-3)+n(n+1)÷(x-3)=n+(n+1)x-3=n或x-3=n+1x=n+3或x=n+4呵呵 我只是没用÷号