First of all, you have to imagine a triangle with a line connecting the two points and a verticle and horizontal line. You know that the lengths of the two shorter lines squared and added together will equal the length of the longer line squared because a^2+b^2=C^2, so you need to find the length of the two shorter lines. One line is 2 long (5-3) and the other is 4 long(2--2).2 sqaured is 4 and 4 squared is 16. 16+4 is 20. The answer is square root twenty.