PSAT 1.8 Math Narrative Walkthrough

PSAT 1.8 Math Narrative Walkthrough. Which description of a circle corresponds to the equation?

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Transcript

00:18

answers Okay so we're looking for the description of a

00:22

circle This is important stuff Because of a circle ever

00:25

hijacks your car you'll want to be able to give

00:27

a clear description Otherwise he might just roll free Were

00:30

given an equation X plus two squared Plus why Plus

00:33

three great design Yeah Kind of like that princes and

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were tasked with finding the answer choice that accurately describes

00:40

that circle But we don't see anything about hair eye

00:42

color here so probably need you bit of math Unfortunately

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not too much though because if we know the standard

00:47

equation of a circle and hopefully we dio then this

00:49

problem is a snap Here it is X minus h

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squared plus y minus k squared equals r square Well

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gee golly will occurs That looks an awful lot like

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our equation already So we really don't have to do

01:02

Too much with it Since the center of a circle

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is represented by the point h k in the standard

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equation we just have to look at the numbers in

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our equation and see how they line up while the

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two here is our age And the three here is

01:13

rk But notice that there are a couple minus signs

01:16

in the standard equation meaning we'll have to change the

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signs on our numbers to making the center of the

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circle negative too negative Three now for the radius which

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is the number on the other side of the equal

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sign But the radius isn't r squared it just plain

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old are so we'll need to reverse the operation here

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Taking the square root of nine You get three just

01:37

to make sure we can plug everything back into the

01:39

standard equation and yep checks out there we go there

01:42

to describe this circle We'd say it has a center

01:44

located at point Negative Too Negative three with a radius

01:47

of three But looks like answer choice d already beat

01:51

us to it Special warning to all you rectangles out

01:53

there Unfortunately you're the number one target of thieving circles

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If you leave your vehicle unattended there's a good chance 00:02:00.402 --> [endTime] That will be a polygon sixty seconds Oh nelly