JEE mathematics

Find the value of x satisfying log₃(x² - 4x + 3) = log₃(x - 1) — JEE Mathematics

NRNikhil Rao · 12 Asked 1mo ago 1,050 views 1 answer

Find the value of $x$ satisfying $\log_3(x^2 - 4x + 3) = \log_3(x - 1)$.

1 Answer

VAVidaara Admin ✓ Vidaara Team ✓ Accepted · 1mo ago ▲ 22

First, find the domain constraints for the logarithms to be defined:

  1. $x^2 - 4x + 3 > 0 \implies (x-1)(x-3) > 0 \implies x \in (-\infty, 1) \cup (3, \infty)$
  2. $x - 1 > 0 \implies x > 1$

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?
Gaurav Pandey · 1mo ago
RV
Can someone explain why we ignore the other root here?
Rohit Verma · 1mo ago
E
This is exactly the kind of step-by-step I needed. Respect.
EthanWalker47 · 1mo ago
PI
Saved me before my mock test. Much clearer than my coaching notes.
Pooja Iyer · 1mo ago
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