谁能帮我解几道极限的题目?

题目

谁能帮我解几道极限的题目?
1 求f(x)=sin2x+tan(x/2)周期
2 lim(x^n-1)/(x-1) (n为正整数)
x-1
3 lim(根号(2x+1)-3)/(根号(x-2)-根号2)
x-4
4 lim(根号(x^2+x+1)-根号(x^2-x+1))
x-正无穷
5 lim{根号[(x+p)(x+q)]-x}
x-正无穷
6 lim(x^2+1)(3+cosx)/(x^3+x)
x-无穷
7 lim(1/(x+1)+1/(x^2-1))
x--1
8 lim(sinx^2-x)/[((cosx)^2)-x]
x-无穷

答案

1 2*pi
2 n
3 (2根号2)/3
4 1
5 (p+q)/2
6 0
7 无穷
8 1