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SAT Math 4.5 Algebra and Functions 197 Views
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Description:
SAT Math 4.5 Algebra and Functions
Transcript
- 00:02
Here’s your shmoop du jour, brought to you by Dollar Signs.
- 00:05
Why can’t there be more of THOSE on the highway?
- 00:08
If x $ y is defined as x $ y equals the square root of x squared minus y squared,
- 00:18
and 13 $ y = 5, what is y?
- 00:22
And here are the potential answers…
Full Transcript
- 00:26
Is it just us are you seeing dollar signs?
- 00:29
So we're given that x $ y equals the square root of x squared minus y squared.
- 00:34
So, 13 $ y is the square root of 13 squared minus y squared.
- 00:43
The given information tells us that 13 $ y equals 5.
- 00:47
This can be written as the equation square root of 13 squared minus y squared equals 5.
- 00:53
This gives us square root of 169 minus y squared equals 5.
- 00:59
Let’s get rid of the square root by squaring both sides.
- 01:02
This gives us 169 minus y squared equals 25.
- 01:07
We add y squared to both sides, then subtract 25 from both sides to get 144 equals y squared.
- 01:14
Now we can take the square root of 144 to get y equals 12.
- 01:18
BUT…we have to remember that negative 12 is also an answer, since a negative, when
- 01:23
squared, is positive.
- 01:24
The answer is (E).
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