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Playlist ACT® Pre-Algebra 34 videos
ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math Pre-Algebra Drill 1, Problem 3. Can you find the product of two square roots?
ACT Math 4.2 Pre-Algebra 390 Views
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Description:
ACT Math: Pre-Algebra Drill 4, Problem 2. What is the fourth term in the series?
Transcript
- 00:03
It's howdy-shmoopy time... It's howdy-shmoopy time...
- 00:07
The first term in a series is the square root of x.
- 00:10
Each subsequent term is determined as the
- 00:12
previous term raised to the power of three-halves. What is the fourth term?
- 00:16
And here are the potential answers...
Full Transcript
- 00:22
Ugh. This one is... ugly. But maybe it's
- 00:25
pretty on the inside. Let's think this one through.
- 00:28
In any question where we have both a fraction AND a square root sign, odds are good that
- 00:33
they are testing us on whether or not we realize that a square root is just the inside part
- 00:37
raised to the one half power.
- 00:40
That is, the square root of x here is the same as x to the one half.
- 00:44
So... now that we are all living in Exponentland...
- 00:47
We have a series of 4 terms... and term 1 here is x to the one half.
- 00:52
Now we raise the power to three-halves for the second term -- and we know -- hopefully
- 00:57
-- that if we are raising exponents to powers we just multiply the exponents...
- 01:01
...so in this case we multiply one half by three halves to get x to the three-fourths
- 01:06
as the second term.
- 01:08
Now do it again to get the 3rd term.
- 01:10
We have x to the three-fourths to the power 3 over 2, which is multiplied to get 3/4 times
- 01:16
three-halves, or 9/8.
- 01:18
Almost to the promised land... located conveniently between Exponentland and Frontierland...
- 01:24
Ok... we have x to the 9/8 to the three-halves, so we multiply 9 over 8 by 3 over 2 to get
- 01:33
27 over 16... or x to the 27/16ths... and the answer is E.
- 01:40
As in, "Exponentland."
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