If 3^(x - y) = 81 and 3^(x + y) = 729 Find value of x*y

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21 Apr 2017 Find the value

If 3^(x - y) = 81 and 3^(x + y) = 729
Find value of x*y

OPtion

1) 1
2) 2
3) 3
4) 4
5) 5
6) 6
7) 7
8) 8
9) 9
10) 10

Solution

3^(x - y) = 3^4
x-y = 4 ---(i)

3^(x + y) = 3^6
x+y = 6 ---(i)

Adding (i) and (ii) and solving we get
x = 5
y = 1

So x*y = 5*1 = 5

Correct Option: 5 Best Solution (0)