Question

In the formula
$log_{a}(xy) = log_{a}(x) + log_{a}(y)$
which of the following is true?
1). x>0, y>0, a=1
2). x<0, y<0, a=1
3). a>0, y>0, x=1
4). x>0, y>0, a not equals to 1
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Answer 1

4) x O, y. 0, a not equals to 1 is true