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TSI Math Videos 144 videos

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TSI Math: One of These Parabolas Is Not Like the Others 3 Views


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Description:

Except for one, all of the following parabolas have the same axis of symmetry. Which one is it?


Transcript

00:02

Okay sy match members We got more quadratic ce for

00:04

you Here we go Except for one All of the

00:07

following paralysis had the same axis of symmetry Which one

00:11

is it If the problem's equation is why equals a

00:18

x squared plus b x plus c like that's the

00:20

standard format for problem than the access of symmetry of

00:23

a parabola is the vertical line x equals negative b

00:26

over two a well assuming this isn't a trick question

00:30

in the same math test is no time for paranoia

00:33

Three of the four parable is shown here need to

00:36

have the same access of symmetry so let's calculate the

00:39

acts of symmetry for the first two choices we've got

00:42

why equals negative three x squared plus for x minus

00:46

five that's a nougat y equal six x squared plus

00:49

eight x plus seven seven b and well let's just

00:51

see what happens if we get the same result We've

00:53

found the access of symmetry common tio three of the

00:57

answer choices So check the other answer choices until we

01:00

stumble on a different answer Yeah we stumble a lot

01:02

around here If we get different results then one of

01:05

the first to answer choices is the exception to the

01:07

norm And that means one of them's The answer Okay

01:10

let's do this thing by the first answer choice has

01:12

an x Squared coefficient equal to negative three and an

01:16

ex coefficient equal toe four So a here is negative

01:19

free and b is for In that case we've got

01:22

negative b over two A there So that gets us

01:24

negative for over two time thing Free or negative for

01:28

negative six or just two thirds Right Well the second

01:30

answer choices a is six there and b is eight

01:34

right there So it's access of symmetry is the formula

01:37

and they're going to be over two way So it's

01:38

negative eight over twelve equals negative two thirds And what

01:44

does that mean Well since we ended up with a

01:46

different result compared to the first choice one of these

01:48

is the exception So it's compared to the third answer

01:51

choice Well a equals fifteen there and b is negative

01:55

Twenty and then we've got a little formula here We

01:58

can plug ins We get negative twenty over too Two

02:00

times fifteen that's thirty and that's Negative of the negative

02:04

twenty over thirty or just positive Two thirds Alright this

02:07

result matches the first answer choice So the second answer

02:10

choice is our exception The answer is b this guy 00:02:13.97 --> [endTime] right here And that's the answer or not

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