The Simple Maths Equation Everyone Seems To Get Wrong (Even Photomath)
The simple equation below seems to always stump people. (And its not the only one)
Upon solving the equation, most people get an answer where x=9 (as does Photomath), but there is another answer to this equation that has been unintentionally ignored.
Sketching the graph on Desmos reveals that x=-7 is also a possible solution.
If you plug x=-7 into the equation you will see that it is definitely a solution, so Desmos has not made a mistake.
When approaching a question like this most people will use this method:
This will give you the answer x=9, but what happened to the x=-7?
Well, what is happening here is you are actually taking the square root of the right hand side, but since you do not see the surd, you completely forget that you must take the negative and positive values of the right hand side.
A better way to approach this question to stop you from forgetting the negative value is to turn the equation into a quadratic:
Using this method, you can ensure that you always account for both solutions of an equation.
It is quite amazing to me that Photomath failed to get the correct answer. So here is your proof, Photomath isn’t always right!
