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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 1.3 Intermediate Algebra 506 Views
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Description:
ACT Math Intermediate Algebra Drill 1, Problem 3. Can you find the value of a in this expression?
- Intermediate Algebra / Quadratic equations (Quadratic Formula)
- Product Type / ACT Math
- Foreign Language / Arabic Subtitled
- Foreign Language / Spanish Subtitled
- Foreign Language / Korean Subtitled
- Foreign Language / Chinese Subtitled
- Algebra / Understand the relationship between zeros and factors of polynomials
- Algebra / Understand the relationship between zeros and factors of polynomials
- Algebra / Solve equations and inequalities in one variable
- Algebra / Solve equations and inequalities in one variable
- Algebra / Solve equations and inequalities in one variable
- Algebra / Solve equations and inequalities in one variable
- Algebra / Understand the relationship between zeros and factors of polynomials
- Intermediate Algebra / Quadratic formula
Transcript
- 00:02
And here's another shmoop de jour...
- 00:04
Solve for a: 2a squared plus 4a minus 1 equals 0.
- 00:08
And here are the potential answers...
- 00:14
Before we even think about starting, we should always glance at the potential answer set first
- 00:19
Here, the numbers scream at us that the quadratic equation will be involved.
Full Transcript
- 00:23
The quadratic equation looks like this:
- 00:26
We are drawing from a line of the equation "ax squared plus bx plus c."
- 00:31
...and we have to figure out what a, b and c are so we can plug them into the right places.
- 00:37
In this case, the 2 comes from here; it's A.
- 00:39
B is here, and it's 4.
- 00:42
And C is here, and it's negative 1.
- 00:45
Now we just plug in the numbers and this is what we get.
- 00:47
Now we just have to simplify. We get negative 4 plus or minus 4 squared which is 16....
- 00:53
...minus 4 times 2, then times negative 1...
- 00:57
... so it's plus 8... and we get negative 4 plus or minus 16 plus 8, or 24, here under
- 01:02
the square root symbol...
- 01:03
...all over 2 times 2, or 4.
- 01:07
Simplify one more time and we have...
- 01:09
Both A -- here... and B -- here.
- 01:12
Answer: D.
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