
2*log 4(4+x)=4-log2(x-2)


Ответы на вопрос




We can solve the equation using algebraic manipulations.
First, we can simplify the left-hand side of the equation using the logarithmic identity log_a(b^c) = c*log_a(b):
2*log_4(4+x) = log_4((4+x)^2)
Next, we can simplify the right-hand side of the equation by using the logarithmic identity log_a(b/c) = log_a(b) - log_a(c):
4 - log_2(x-2) = log_2(16) - log_2(x-2) = log_2(16/(x-2))
Substituting these simplifications back into the original equation, we get:
log_4((4+x)^2) = log_2(16/(x-2))
To solve for x, we can use the property that if two logarithms with the same base are equal, then their arguments must be equal. Thus:
(4+x)^2 = 4/(x-2)
Expanding the left-hand side and simplifying, we get:
x^2 + 8x + 16 = 4/(x-2)
Multiplying both sides by (x-2), we get:
x^3 - 6x^2 - 8x + 32 = 0
We can use synthetic division to factor the polynomial:
2 | 1 -6 -8 32 | 2 -8 0 | 1 -4 -16
Thus, the polynomial factors as:
(x - 2)(x^2 - 4x - 16) = 0
Using the quadratic formula to solve for the roots of the quadratic factor, we get:
x = 2, 2 + 2sqrt(5), 2 - 2sqrt(5)
However, we need to check which solutions satisfy the original equation, as some solutions may result in undefined or extraneous values.
For x = 2, we have:
2log_4(4+2) = 2log_4(6) = 2*log(6)/log(4) ≈ 2.79
4 - log_2(2-2) = 4
Thus, x = 2 is a valid solution.
For x = 2 + 2*sqrt(5), we have:
2log_4(4+2+2sqrt(5)) ≈ 3.34
4 - log_2(2+2*sqrt(5)-2) ≈ -0.86
Thus, x = 2 + 2*sqrt(5) is not a valid solution.
For x = 2 - 2*sqrt(5), we have:
2log_4(4+2-2sqrt(5)) ≈ -0.73
4 - log_2(2-2*sqrt(5)-2) ≈ -4.61
Thus, x = 2 - 2*sqrt(5) is not a valid solution.
Therefore, the only valid solution is x = 2.


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