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SAT Math 9.6 Algebra and Functions 275 Views
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SAT Math 9.6 Algebra and Functions
Transcript
- 00:03
Here’s your shmoop du jour, brought to you by Absolute Value.
- 00:07
Putting the “abs” in “absolute.”
- 00:10
| 3x squared + 2x | = 8
- 00:15
What is the largest possible value for x?
- 00:20
Okay, so…while x may be equal to more than one value, the only correct answer is the largest.
Full Transcript
- 00:26
Let’s keep that in mind. First, remember that,
- 00:29
when solving absolute value equations, we split them into the two possibilities.
- 00:33
The number under the absolute value is either positive or negative 8.
- 00:37
Let’s start with 3x squared + 2x = 8. We subtract 8 from both sides, and get 3x squared + 2x – 8 = 0.
- 00:46
Then, it’s just a simple matter of using the quadratic formula.
- 00:49
Plugging in our values and solving...
- 00:57
...we get that x can be either 4/3, or -2.
- 01:01
Remember we want the largest, so -2 is out.
- 01:05
The other equation is 3x squared + 2x = -8.
- 01:09
We add 8 to both sides to get our quadratic.
- 01:12
Then, we use the quadratic formula again to find x.
- 01:16
But when we actually try to plug our numbers into the quadratic formula, we see that we’re
- 01:20
trying to take the square root of -92.
- 01:23
Uh, good luck with that. Turns out there is no real solution to this equation.
- 01:27
And since there are no real solutions… the only possible answers
- 01:30
come from solving 3x squared + 2x = 8.
- 01:33
So our answer is 4/3.
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