Logarithm Equation Question 2 [Checking validity of answers in logarithms equations]


Solve the equation

\lg(3a+2)+ lg(5a-3)=1+ 2lg (a)

Ans : a = 1 or -6/5

Question : Do we need to include -6/5

Contributed by YC

It is important for you to check if your answers are valid i.e are there any answers you would need to reject?
This is what I called checking for validity of answers.

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5 Responses to Logarithm Equation Question 2 [Checking validity of answers in logarithms equations]

  1. Clearly the domain (admissible values of x for the argument of the function f(x)=lg(x)) of f(x) is (0, \infty). If a=-6/5, then 3a+2 is negative; therefore x=-6/5 is not admissible into the domain of function f(x).

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