When a function and its inverse intersect what must be true about the point of intersection

What ia the sum if the first 7 terms of the geometric series

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b

Ahighway between points a and b has been closed for repairs. an alternative route between there two locations is to travel between a and c and then from c to b what is the value of y and what is the total distance from a to c to b?