stolyar wrote:

Find the integer K:

(1) K*|K|=4

(2) |K|*|K|=4

from i, if k = -2, K*|K|= -4 which is not true.

if k = 2, K*|K|= 4 which is true. so the only possible value of k =2.

from ii, if k = 2, K*|K|= 4 which is true.

if k = -2 2, K*|K|= 4 which is also true. so here k can be + or - 2.

so only A is sufficient.

gmat_crack wrote:

stolyar wrote:

A is correct

Can someone explain Why A

My logic is

K*|K| = 4

so |K| = +K if K > 0

= -K if K < 0

case 1 K > 0:

K * |K| = K * K = 4 ---> K^2 = 4 ---> K = +/- 2

Since K has two values so its not possible.

For case 2 K < 0

|K| = -k

==> K* (-k) = -K^2 = 4 -->>> which doesn't make any sense.

Can someone point out flaw in my derivation