# 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.

### Related Post

Logarithm Equation Question 1 I met a student and she passed me this paper with this Lg question on it, asking me on the solution for solving this equation : Coincidentally, I w...
Revisit: A-Math Logarithms Equations (Plus: Types of Equations & How To Identify Them Easily) With the school holidays period at this moment, it is perhaps a good time to revisit some of the 'killer' topics in O Level Math. I will start off w...
Download your set of Logarithms Questions Free! In conjunction with celebrating the 100th post on singaporeolevelmaths.com, I have prepared a set of logarithms questions for all of you. Those who...
O level A-Math: Fatal Mistake In Logarithm Equation You Must Aviod This is a common mistake I notice in my O level A-Math essential concepts revision workshop. Solve the following equation: First, you must i...
Linear Law,Just 1 Strategy Makes A Grade Difference What is Linear Law? It is a tool which will allow you to transform non-straight line equation to straight line equation so that you can plot a stra...

### Ai Ling Ong

Hi, I'm Ai Ling Ong. I enjoy coaching students who have challenges with understanding and scoring in 'O' Level A-Maths and E-Maths. I develop Math strategies, sometimes ridiculous ideas to help students in understanding abstract concepts the fast and memorable way. I write this blog to share with you the stuff I teach in my class, the common mistakes my students made, the 'way' to think, analyze... If you have found this blog post useful, please share it with your friends. I will really appreciate it! :)

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

1. Humairah says:

I guess, we do not include -6/5 as there is no such graph of log(-a).