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ACT Math 4.2 Intermediate Algebra 433 Views


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ACT Math: Intermediate Algebra Drill 4, Problem 2. What is the root of this equation?

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English Language

Transcript

00:02

And here is your shmoop de jour...

00:06

What is a root of this equation? y2 - y = 4

00:10

And here are the potential answers...

00:16

OK so what is this question asking?

00:18

Sneaky quadratic equation question. We need to pull the root numbers and plug them in

00:25

and see what we get. Remember the quadratic equation? Our old buddy,

00:29

old pal? When an equation is in the form ax squared

00:33

plus bx plus c equals 0... ...the solution can be negative b plus or

00:39

minus radical, b-squared minus 4ac all over 2a.

00:45

That's the quadratic equation formula.

00:47

That's a mouthful. Let's change the equation to y squared minus y minus

00:57

4 equals 0... so it looks like ax squared plus bx plus c equals 0.

01:06

We can see that a is 1, b is negative 1, and c is negative 4.

01:11

When we start pluggin', we get that 1 plus or minus the square root of 1 minus 4 times

01:22

1 times negative 4 all over 2... ...gives us 1 plus or minus the square root

01:29

of 17 over 2. So now we have one solution, or root, of the equation.

01:34

Looks like D.

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