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Express a in terms of b in the following: 2 ⁢log a − 1/3 ⁢log ⁡b = 2 - Mathematics

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Question

Express a in terms of b in the following:

`2 log a - 1/3 log b = 2`

Sum
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Solution

Given: `2 log a - 1/3 log b = 2`

To find: Express a in terms of b.

Calculation:

Step 1: Using the rule n log ⁡x = log ⁡xn,

`log a^2  -  log b^(1/3) = 2`

Step 2: Using the rule log m − log ⁡n = `log ⁡(m/n)`,

`log (a^2/b^(1/3)) = 2`

Step 3: We know that 2 = log ⁡100  ....(Since the base is 10.)

So, `log (a^2/b^(1/3)) = log 100`

Step 4: Since the logarithms are equal, their arguments are equal:

`(a^2/b^(1/3)) = 100`

Step 5: Multiply both sides by `b^(1/3)`:

`a^2 = 100 b^(1/3)`

Now, take the square root of both sides:

a = `sqrt(100b^(1/3))`

a = `10b^(1/6)`

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Chapter 7: Logarithms - EXERCISE 7B [Page 75]

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B Nirmala Shastry Mathematics [English] Class 9 ICSE
Chapter 7 Logarithms
EXERCISE 7B | Q 9. (ii) | Page 75
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