询问几道高一数学题^^HELP!
1.设f(x)=(4^x)/(4^x+2)
求和:f(1/2007)+f(2/2007)+...+f(2006/2007)
2.已知向量a=(cos(3x/2),sin(3x/2)),b=(cos(x/2),-sin(x/2)),x∈【-兀/3,兀/2】.若|a+b|=1/3,求cosx的值.
3.已知实数x,y满足y=根号里边(3-x^2),试求m=(y+1)/(x+3)及b=2x+y的取值范围.