calculus
posted by sara .
If f(1) > 0 and f(3) < 0, then there exists a number c between 1 and 3 such that f(c) = 0. Is this true or false?
Please and thank you

Absolutely true, uuuuhhh, if f(x) is continuous.

Can you please explain why it is true
Please and Thank you 
If the curve is continuous, and at x=1 f(x) is positive, and at x=3, f(x) is negative, somewhere it crossed the axis.