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:

image

First, you must identify the type of question since different types of question require different strategies.
It's a different log-log question.
Strategy required: Change base.

image
Change base formula used.
Reason for changing to base 2: Between changing to base 2 or x, we choose base 2 as x is an unknown, we choose not to work with THE unknown most of the time, don't we?

image

Since we observe that there is a common term (log2 x),
image
image Did you observe the fatal mistake (It's #7 Common mistake in Logarithm?

image
The correct way to do the substitution would be:
image

image

image
Solve the quadratic equation for y. Substitute the value back to find x.

Remember to check for validity of answers.

Related Post

Top 7 Commonly Made Mistakes in Logarithm How many of you would like to learn Math faster? And how many of you would like to score more marks for Math? Do you know that one of the fastest ...
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...
Logarithm Equation Question 3 This is an interesting question which I came across under Additional Mathematics (A-Math): Find the value of x. Who is courageous to work on...
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...
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...

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! :)

2 Responses to O level A-Math: Fatal Mistake In Logarithm Equation You Must Aviod

Leave a reply