有括号吗?如果没有括号的话,只要n是偶数即可.如：n=2：7*2+(19/2)*2+1=14+19+1=34n=4：7*4+(19/2)*4+1=28+38+1=67.如果有括号：(7n+19)/(2n+1)=(6n+3+n+16)/(2n+1)=(6n+3)/(2n+1)+(n+16)/(2n+1)=3+(n+16)/(2n+1) &nb...有括号的(7n+19)/(2n+1)