Question

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

Answer 1

Answer:

Step-by-step explanation:

3^(x-y) = 81

3^(x-y) = 3^4

Comparing exponents

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

3^(x+y) = 729

3^(x+y) = 3^6

Comparing exponents

x+y = 6 -----------(ii)

Adding eqn(i) and eqn(ii)

2x = 10

x = 5

Substituting value of x in eqn(ii)

y = 1

Answer 2

Answer:

x = 5

y = 1

Step-by-step explanation:

3^(x-y) = 81

3^(x-y) = 3^4

Comparing exponents

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

3^(x+y) = 729

3^(x+y) = 3^6

Comparing exponents

x+y = 6 -----------(ii)

Adding eqn(i) and eqn(ii)

2x = 10

x = 5

Substituting the value of x in equation(ii)

y = 1