# Math Help - Calculus, double integral problem

1. ## Calculus, double integral problem

Hey there I need some help with this problem.

Let f be continuous on [a,b] and g continuous on [c,d]. Show that:

where R = [a,b] X [c,d]

Please explain each step so that I can understand this problem better thanks!

2. ## Re: Calculus, double integral problem

Hey gfbrd.

Hint: Try integrating out one of the variables (either x or y) and bring this constant outside the final integral (which will be with respect to the other variable). Once you do this, substitute the old integral in for the constant and you are done.

So as an example Integral Integral f(x)g(y)dxdy = c*Integral g(y)dy. What is c in terms of the integral of f(x)dx?

3. ## Re: Calculus, double integral problem

Edit: hahha nevermind! I figured it out thanks!

4. ## Re: Calculus, double integral problem

If you integrated out for example f(x)dx over some range you will get F(b) - F(a) as your constant c.