Quadratic Equations
Exponential Equation — Sum of Solutions
nta_pyq_2024_apr
Grade 11
Question:
The sum of all the solutions of the equation $(8)^{2x}-16\cdot(8)^x+48=0$ is:
$1+\log_8(6)$
$1+\log_6(8)$
$\log_8(6)$
$\log_8(4)$
Step-by-Step Solution
Key Concept: Let $t=8^x$: $t^2-16t+48=0\Rightarrow t=4$ or $t=12$. So $8^x=4\Rightarrow x=\log_8 4$ and $8^x=12\Rightarrow x=\log_8 12$.
Sum $=\log_8 48=1+\log_8 6$.
Correct Answer: 1