maths ...urgent

Posted by gauri on Feb 18, 2013; 1:13pm
URL: http://discussion-forum.276.s1.nabble.com/maths-urgent-tp7579745.html

let f be a real valued differentable function defined for all x>=a.
consider F defined by F(x)= integration f(t) dt from a to x.
if f is increasing on any interval,then on that interval F is:

convex
concave
increasing
decreasing.

the answer is convex but someone please explain how and why?