Theory➡ Larger(a,b) <= LCM (a,b) <= a*b
Which of the following CANNOT be the least common multiple of two positive integers x and yLet's take each option choice and evaluate
(A) xyNow, we can take co-prime values of x and y (co-primes are numbers which have only 1 as as the common factor) and this will be true.
Ex, x=2 and y=3 => LCM = 2*3 = x*y
=>
TRUE(B) xThis can be true when one number is x and other number is \(\frac{x}{2}\)
Example: One number is 2 (which is \(\frac{x}{2}\)) and other number is 2*2 = 4 (which is x)
=>
TRUE(C) yThis can be true when one number is y and other number is \(\frac{y}{2}\)
Example: One number is 2 (which is \(\frac{y}{2}\)) and other number is 2*2 = 4 (which is y)
=>
TRUE(D) x - yNow. LCM ≥ larger of the two numbers x and y
Since, x and y are positive so x-y will be lesser than the larger of x and y
=> LCM cannot be x-y
=>
FALSEWe don't need to check further, but I am solving to complete the solution.
(E) x + yCouldn't think of any value of x and y for which LCM(x,y) = x + y
We might have to edit this option choice to 2x or 2y or some valid LCM or need to delete this option choice.
=>
FALSESo,
Answer will be D or E.
Hope it helps!
Watch the following video to Learn the Basics of LCM and GCD