2019 · Q12
Which of the following pair of numbers is the solution of the equation 3^(x+2) + 3^(-x) = 10?
Elementary MathematicsAlgebra
- A0, 2
- B0, -2
- C1, -1
- D1, 2
Explanation
Put y = 3^x: 9y + 1/y = 10 ⇒ 9y^2 − 10y + 1 = 0 ⇒ y = 1 or y = 1/9. y = 1 gives x = 0 and y = 1/9 gives x = −2. The solution pair is (0, −2).