Question

If x + 3 is a multiple of 3, which of the

following is not a multiple of 3?
(A) x
(B) x + 6
(C) 6x + 18
(D) 2x + 6
(E) 3x + 5

Answer 1

If integer m is not a multiple of 3, which of the following must be true? ... of 2 let m=3K+2, (m+1)(m-1) = (3K+3)X(3K+1) is a not a multiple of 2

Explanation:

m=4 or 5 satisfies the equation (m+1)(m-1) is a multiple of 3. Hence true.

m=4, (m+1)(m-1) = (4+1)(4-1)=15, not multiple of 2.

Answer 2

The answer is E because if x+3=0 then x=-1 which is the multiple of 3x-1
1)x
we have x so its -3
2)x+6
-3+6=3 its a multiple of 3 (3x1)
3)6x+18
6(-3)+18
0 is a multiple of 3 (3x0)
4)2x+6
2(-3)+6
0 is a multiple of 3
5)3x+5
3(-3)+5
-1 is not a multiple of 3