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ACT Mathematics Videos 164 videos
ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?
ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.
ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math 3.3 Elementary Algebra 233 Views
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Description:
ACT Math Section: Elementary Algebra Drill 3, Problem 3. Solve for x.
- Elementary Algebra / Solving simple quadratic equations
- Product Type / ACT Math
- Foreign Language / Arabic Subtitled
- Foreign Language / Korean Subtitled
- Foreign Language / Chinese Subtitled
- Foreign Language / Spanish Subtitled
- Algebra / Solve equations and inequalities in one variable
- Algebra / Solve equations and inequalities in one variable
- Algebra / Use polynomial identities to solve problem
- Algebra / Solve equations and inequalities in one variable
- Algebra / Solve equations and inequalities in one variable
- Algebra / Use polynomial identities to solve problems
- Elementary Algebra / Solve quadratic equations by factoring
Transcript
- 00:03
And here is your shmoop de jour.
- 00:05
Solve for x: x squared plus 6x plus 8 equals 0
- 00:09
And here are the potential answers...
- 00:16
OK. Any time we see equations in this format -- where there's an x squared then and
- 00:21
x then an integer -- odds are high that they're asking us to factor.
Full Transcript
- 00:25
What 2 numbers can be multiplied to get 8... and can also be added to get 6?
- 00:31
Well, the factors of 8 are 1 and 8; that won't work...
- 00:38
...what about 2 and 4? Ding ding ding!
- 00:40
So... 2 times 4 is 8... and 2 PLUS 4 is 6... so we can just rewrite the factored version as
- 00:49
The quantity x plus 2 times the quantity x plus 4... equals zero.
- 00:54
Now if either of these guys is 0, the whole equation is zero because zero times anything...
- 00:59
is zero. Yeah, it brings everyone else down to its level.
- 01:00
So if x is negative 2, this part is 0... and if x is negative 4, this part is 0.
- 01:06
x has to be one of those answers... and OUR answer here is either A or B... which is...
- 01:11
option D. Done
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