How many ordered pairs such that is a positive real number and is an integer between and , inclusive, satisfy the equation
Pick one
Solution
By the properties of logarithms, we can rearrange the equation to read with . If , we may divide by it and get , which implies . Hence, we have possible values , namely
Since is equivalent to , each possible value yields exactly solutions , as we can assign to each . In total, we have solutions.
Want a route through all this instead of an archive? The track
puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.