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CAHSEE Math 2.2 Mathematical Reasoning 282 Views

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Description:

Mathematical Reasoning: Drill Set 2, Problem 2. A positive integer, n, when squared, is always greater than or equal to the doubling of n, except when n equals...what?

Language:

English Language

Subjects:

Tags:

Mathematical Reasoning / Generalizing results

Common Core Standards:

Transcript

00:02
Here's an unshmoopy question you'll find on an exam somewhere in life...
00:06
A positive integer, n, when squared, is always greater than or equal to the doubling of n,
00:11
except when n equals... what?
00:14
And here are the potential answers...
00:21
Okay, so this question just asks us to try a few random numbers to

00:24
see whether we can conceive the theory of n in our brain.
00:29
When we get these kinds of problems, always
00:31
try 0 first because it's usually really easy to manipulate.
00:35
Then 1. Then negative 1. Then a fraction. Annnnnd we're done. Usually.
00:41
In this case, note the word ALWAYS and greater than or equal to...
00:45
It's giving us the equation n squared is greater than or equal to 2n.
00:50
True for 0. True for 2. True for 4. True for one half? No.
00:55
Try 1. Well, 2n is 2 and 1 squared is...1. So it's the only one that's NOT true --
01:05
And the answer is A.
Full Transcript