this is the way to do: now as the thing r^5 is in the lcm thus at least one no.must have r^5 as its factor. thus let p has r^5 as one of its factors and q can have r^0 or r^1 or r^2 or r^3 or r^4 or r^5 as its factors. similarly q has one of its factors r^5 and p has r^0 or r^1 or r^2 or r^3 or r^4 or r^5 as factors. thus total 9 cases not ten as we wont count the case twice which is p = q = r^5. similarly u can do with t . final answer: this is for cases of (x,y) ordered duplet extend by taking cases for three nos.
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