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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?

Language:
English Language

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.

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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