jainpiyushjain wrote:
If x and y are distinct factors of 24, then which of the following CANNOT be a factor of 24?
I. (x+y)2
II. x2−y2
III. xy+y2
A. I only
B. I and II only
C. II and III only
D. II only
E. III only
OA A
Try to DISPROVE I, II and III by showing that each CAN be a factor of 24.
Plug in the smallest possible values for x and y, since small values are more likely to divide into 24.
If we plug x=2 and y=1 into I, II and III, we get:
I: (2+1)² = 9, which is not a factor of 24.
Hold onto I.
II: 2² - 1² = 3, which is a factor of 24.
Eliminate B, C and D, each of which includes II.
III: 2*1 + 1² = 3, which is a factor of 24.
Eliminate E, which includes III.
The correct answer is
A.
No need to worry about why answer choice I cannot be a factor of 24, since
A is the only remaining answer choice.
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