Question

3√7 please help I dont understand

Answer 1

What is log675 with base 5 × log 3 with base 3?
We have to calculate (log 675 to the base 5) × (log 3 to the base 3)

Note the following important points :

(1.) log 675 to the base 5

=> log 675 to the base ‘e’ / log 5 to the base ‘e’

=> ln 675 / ln 5

Since 675 = 5^2 × 3^3

=> ln 675 = ln [5^2 × 3^3]

=> ln (5^2) + ln (3^3)

=> 2 ln 5 + 3 ln 3

Hence, log 675 to the base 5

= ln 675 / ln 5

= [2ln 5 + 3ln 3] / ln 5

(2.) Similarly, log 3 to the base 3

=> Since the logarithm of any natural number 'x' to the base of same number 'x' is always 1 (since any natural number raised to the power '1′ is equal to the same number) ,

Thus, (log 3 to the base 3) = 1

Hence, our problem reduces to:

(log 675 to the base 5) × (log 3 to the base 3)

=> [(2ln 5 + 3ln 3) / ln 5] × (1)

=> (2ln 5 + 3ln 3) / ln 5

=> So we only require the values of natural logarithm of 3 and 5 :)

We should remember these values, or we can always use log table.

Since ln 3 = 1.098

and ln 5 = 1.609

=> 2ln 5 = 2(1.609) = 3.218

=> 3ln 3 = 3(1.098) = 3.294

Hence,

solution : (3.218 + 3.294) / 1.609

=> 6.512 / 1.609

=> 4.047

GLAD TO HELP YOU ;))