2. Is a product of three integers XYZ a prime?
(1) x=-y --> for xyz to be a prime z must be -p AND x=-y shouldn't be zero. Not sufficient.
(2) z=1 --> Not sufficient.
(1)+(2) x=-y and z=1 --> x and y can be zero, xyz=0 not prime OR xyz is negative, so not prime. In either case we know xyz not prime.
i did not understand the explanation you gave..... a prime is a number which is divisible by 1 and itself right? if x,y,z are three integers..... and for it to be prime.... two for those three integers should be 1 or -1 or 1,-1.... so the third one be prime number or negative prime number....
(1) says two of them are equal in magnitude... so z can be -p to be prime or negative composite number or positive non prime in either case not sufficient...
(2) z=1 nothing said about x,y..... not sufficient
(1) + (2)product will be a positive
or negative composite number or 1
..... so not a prime which is sufficient....
am i thinking correctly?
, thus it cannot be a prime number (only positive numbers are primes).