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If y>0,y > 0, and log⁡y(x)=4,log⁡10y(25x)=2\log_{y}(x) = 4, \log_{10y} (25x) = 2 hold, what is y?y?

Solution

✅ Correct Option: 1

From log⁡y(x)=4\log_y(x) = 4:

x=y4x = y^4


From log⁡10y(25x)=2\log_{10y}(25x) = 2:

25x=(10y)225x = (10y)^2

25x=100y225x = 100y^2


Substituting x=y4x = y^4:

25(y4)=100y225(y^4) = 100y^2

25y4=100y225y^4 = 100y^2


Dividing both sides by 25y225y^2 (since y>0y > 0):

25y425y2=100y225y2\dfrac{25y^4}{25y^2} = \dfrac{100y^2}{25y^2}

y2=4y^2 = 4

Since y>0y > 0:

y=2y = 2

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