Solve the equation log⁡3x−3log⁡x9=1\log_3 x - 3\log_x 9 = 1.

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Worked solution

5

1. Change the base of the second logarithmic term to base 3

log⁡x9=log⁡39log⁡3x=2log⁡3x\log_x 9 = \frac{\log_3 9}{\log_3 x} = \frac{2}{\log_3 x}

2. Substitute into the equation and form a quadratic equation

Let y=log⁡3xy = \log_3 x.
y−3(2y)=1y - 3\left(\frac{2}{y}\right) = 1
y−6y=1y - \frac{6}{y} = 1
y2−y−6=0y^2 - y - 6 = 0

3. Solve the quadratic equation

(y−3)(y+2)=0(y - 3)(y + 2) = 0
y=3y = 3 or y=−2y = -2

4. Solve for $x$ using the definition of logarithms

When y=3y = 3:
log⁡3x=3  ⟹  x=33=27\log_3 x = 3 \implies x = 3^3 = 27

When y=−2y = -2:
log⁡3x=−2  ⟹  x=3−2=19\log_3 x = -2 \implies x = 3^{-2} = \frac{1}{9}

Answer

x=27x = 27 or x=19x = \frac{1}{9}

AI analysis — may contain mistakes.

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