3个连续自然数是n-1,n.n+1n-1+n+n+1=3n所以是3的倍数3个连续奇数是2n-1,2n+1,2n+32n-1+2n+1+2n+3=6n+3=3(2n+1)所以是3的倍数3个连续偶数的和2n-2,2n,2n+22n-2+2n+2n+2=6n=3×2n所以是3的倍数
