Bunuel
m is negative, and n is an integer. Is m^n positive?
(1) m is odd.
(2) n is odd.
Given: m is negative, and n is an integer.Target question: Is m^n positive?-----------------ASIDE--------------------------------------------------
Two important rules:
ODD exponents preserve the sign of the base. So, (
NEGATIVE)^(
ODD integer) =
NEGATIVEand (
POSITIVE)^(
ODD integer) =
POSITIVEAn EVEN exponent always yields a positive result (unless the base = 0)
So, (
NEGATIVE)^(
EVEN integer) =
POSITIVEand (
POSITIVE)^(
EVEN integer) =
POSITIVE--------------------------------------------------------------------------
Since we're told m is NEGATIVE, we know that, if n is ODD, then m^n will be NEGATIVE, and if n is EVEN, then m^n will be POSITIVE Statement 1: m is odd.Since we don't have any information about whether n is ODD or EVEN, statement 1 is NOT SUFFICIENT.
For example, if m = -1 and n = 1, then
m^n is negativeConversely, , if m = -1 and n = 2, then
m^n is positive Statement 2: n is oddSo, m^n = NEGATIVE^ODD = negative
The answer to the target question is
m^n is definitely NOT positiveSince we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: B