Lesson: The Something Method

Comment on The Something Method

Brilliant!!

Awesome!

This is the best technique so far!

Wow! Thank You.

The technique seems promising. However, I have a small confusion. Since (y/x) = 1 here, why is (x/y)=1 not true for all values of x and y? Can you kindly enlighten me?
greenlight-admin's picture

Hi Sajid,

How did you conclude that (y/x) = 1?

IF it were true that y/x = 1, then it would also be true that x/y = 1.
However, cannot conclude that y/x = 1 (as you suggest)

For example, one solution to the equation is x = 1/2 and y = 2
Notice that these values don't satisfy the equation y/x = 1

Cheers,
Brent

This is awesome. I solved by cross multiplying but this is quicker

Hi brent

In the above question, I have one more technique which is even more faster. that is to blindly assume 1/x=1 and y=1 and substitute in the given eqn. After substitution it seems good. So obviously 1/x=y => xy=1. Though this approach avoids the deep analysis of the numbers in the given eqn, this may not work for all the questions.
greenlight-admin's picture

Hi Vineet,

Good idea.
The main problem with your approach is that it relies on assuming values that satisfy the given equation.

You randomly chose 1/x = 1 and y = 1.
These values just happen to satisfy the given equation.

If you had chosen different values like 1/x = 2 and y = 1, then those values would NOT satisfy the equation, in which case you wouldn't be able to identify the correct answer.

Cheers,
Brent

Amazing.

I love this method, but I'm wondering if there are certain "triggers" or elements to look for in an expression or question that indicate using this method is a good idea. Are there certain cases where using it is especially beneficial, or easy ways to recognize when it's best to employ it?
greenlight-admin's picture

Great question!
I'd say that it's useful when there is a some algebraic expression (e.g., 3xy or 5z or 4w²-19, etc) sitting the place where we typically see just one number.

For example, 13.6^(4w²-19) = 1
Here, we have the expression 4w²-19 representing the exponent of 13.6
So, we might look at this as: 13.6^(something) = 1 and go from there.

Does that help?

Cheers,
Brent

Yes, that's helpful, thank you!

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