Вопрос от Анонимного юзера 15 октября 2024 12:02
Log3 (x3 -x) - log3 x = log3 3;

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15 октября 2024 12:02
To solve the equation ( \log_3 (x^3 - x) - \log_3 x = \log_3 3 ), we can use the properties of logarithms.
First, we can combine the logarithms on the left side using the property:
[ \log_a b - \log_a c = \log_a \left( \frac{b}{c} \right) ]
Applying this property, we get:
[ \log_3 \left( \frac{x^3 - x}{x} \right) = \log_3 3 ]
Simplifying the left side:
[ \frac{x^3 - x}{x} = x^2 - 1 ]
So we can rewrite the equation as:
[ \log_3 (x^2 - 1) = \log_3 3 ]
Since the logarithms are equal, we set the arguments equal to each other:
[ x^2 - 1 = 3 ]
Now, we can solve for ( x ):
[ x^2 = 4 ]
Taking the square root of both sides gives us:
[ x = 2 \quad \text{or} \quad x = -2 ]
However, we must consider the domain of the original logarithmic expressions. The domain requires that the arguments of all logarithmic functions be positive:
- ( x > 0 ) for ( \log_3 x )
- ( x^3 - x > 0 ) which factors as ( x(x^2 - 1) = x(x - 1)(x + 1) > 0 ).
Analyzing the factor ( x(x - 1)(x + 1) > 0 ):
- The critical points are ( x = -1, 0, 1 ).
- The intervals to test are ( (-\infty, -1) ), ( (-1, 0) ), ( (0, 1) ), and ( (1, \infty) ).
Evaluating these intervals shows:
- In ( (-\infty, -1) ): all factors are negative, product is negative.
- In ( (-1, 0) ): one factor is negative, two are positive, product is negative.
- In ( (0, 1) ): ( x > 0 ), ( x - 1 < 0 ), and ( x + 1 > 0 ), product is negative.
- In ( (1, \infty) ): all factors are positive, the product is positive.
Thus, the only valid solution in the domain is ( x = 2 ).
Therefore, the solution to the equation is:
[ \boxed{2} ]
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