If f and g are integers, is fg + 2 prime?

Question

(1) f is odd.
(2) g is even.

Bunuel · Answer

Even when we take the statements together they are not sufficient to answer the question:

If f is any odd number and g=0, then fg+2=2=prime;
If f is any odd number and g=2, then fg+2 is some even number other than 2, thus not a prime.

Answer: E.

sghoshgt · Answer

If we combine both the statement i.e f is odd and g is even in that case it is clear that fg+2 will be any even number other 2. Bunuel can you please help.

Bunuel · Answer

The solution gives an example:
If f is any odd number and g=0, then fg+2 = 2 = prime;

KrishnakumarKA1 · Answer

Given: ‘f’ and ‘g’ are integers.
To find: Is fg+2 prime?
Analysis of statement 1: f is odd.
Let’s draw a table:

Attachment:

table.PNG [ 12.63 KiB | Viewed 5846 times ]

Hence statement 1 is not sufficient to answer. We can eliminate the options A and D.
Analysis of Statement 2: g is even
Let’s draw a table:

Attachment:

table 1.PNG [ 11.78 KiB | Viewed 5837 times ]

Hence statement 2 is not sufficient to answer. We can eliminate the options B
Combining the 1 & 2 statements: we get:
Even after combining we cannot answer the question whether fg + 2 is prime or not.
The correct answer option is “E”.

ksrutisagar · Answer

For Ex : f = 1, g =0 fg + 2 = 0 +2 = 2 , Prime
 
 f = 1, g = 2 then fg + 2 = 2 + 2 = 4 , an even number other than 2 , Not a Prime

Not Sufficient

Choice E

Hope it is clear

ajaanrkhan · Answer

Bunuel , combining the two statements makes it clear that fg+2 is an even number (not 2), so isn't it sufficient to say that, "fg+2 is NOT a prime"? So why is the answer E?

Bunuel · Answer

If f and g are integers, is fg + 2 prime?

(1) f is odd.
(2) g is even.

The solution above clearly give an example:

If f is any odd number and g=0, then fg + 2 = 2 = prime.

bumpbot · Answer

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If f and g are integers, is fg + 2 prime?

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