Find the value of $x$ satisfying $\log_3(x^2 - 4x + 3) = \log_3(x - 1)$.
Find the value of $x$ satisfying $\log_3(x^2 - 4x + 3) = \log_3(x - 1)$.
1 Answer
VAVidaara Admin
✓ Vidaara Team
✓ Accepted
· 3mo ago
▲ 22
First, find the domain constraints for the logarithms to be defined:
- $x^2 - 4x + 3 > 0 \implies (x-1)(x-3) > 0 \implies x \in (-\infty, 1) \cup (3, \infty)$
- $x - 1 > 0 \implies x > 1$
Intersecting these two conditions gives the domain: $x > 3$.
Now equate the arguments:
$$x^2 - 4x + 3 = x - 1$$
$$x^2 - 5x + 4 = 0$$
$$(x - 1)(x - 4) = 0 \implies x = 1 or x = 4$$
Comparing with our domain condition ($x > 3$), $x = 1$ is excluded.
Therefore, $x = 4$.
Answer: 4
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Discussion (4)
GP
Quick doubt: would this method still work if the numbers were not so clean?
RV
Can someone explain why we ignore the other root here?
E
This is exactly the kind of step-by-step I needed. Respect.
PI
Saved me before my mock test. Much clearer than my coaching notes.