Which set of conditions must a function f satisfy so that the convergence of n=1∑∞f(n) can be determined by comparing it to ∫1∞f(x)dx?
a) f is positive, continuous on [1,∞), and f′(x)<0 for all x>1.
b) f is positive, continuous on [1,∞), and decreasing on (1,∞).
c) f is non-negative, continuous on [1,∞), and x→∞limf(x)=0.},{
d) f is positive and continuous on [1,∞).