(2014•顺义区一模)已知函数f(x)=12ax2-x+lnx(a∈R,a≠0)
(Ⅰ)当a=2时,求曲线y=f(x)在(1,f(1))处的切线方程;
(Ⅱ)若在区间[1,+∞)上函数f(x)的图象恒在直线y=ax下方,求a的取值范围.