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PSAT 1.3 Math Diagnostic 245 Views


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Description:

PSAT 1.3 Math Diagnostic. Which of the following most nearly represents the line of best fit?


Transcript

00:00

Thank you We sneak and here's your shmoop du jour

00:05

brought to you by chlorophyll Try telling these guys it's

00:08

Not easy being green Check out this diagram and passage

00:13

right with diagrams Relation All right Which of the following

00:19

most nearly represents the line of best fit All right

00:23

here the potential answer will you Okay we're usually more

00:29

concerned with which pair of pants represents the line a

00:31

best fit but well anything we can wear without having

00:34

a suck in our guts it's high marks from us

00:37

but okay so we've got this graph here and there's

00:39

a red line going across it That's the line of

00:42

best fit if ever there was one Our mission we

00:45

choose to accept it is to figure out which one

00:47

of these four line equations represents that line All right

00:52

if we're interested in any of them representing us while

00:54

we get their business card afterwards okay so the first

00:57

thing we should notice is that this line moves downward

01:00

from left to right indicating a negative slope Unfortunately for

01:04

us it doesn't help us rule out any of the

01:06

answer choices since all four of them have a negative

01:09

sign in front of the ex term right there meaning

01:11

they're all equations for lines with negative slopes Well great

01:15

guess we're gonna have to do this the hard way

01:17

We're told two of the points that fall along the

01:20

line at one point five and sixteen point too and

01:23

then more fifteen point seven six oh goody decimals should

01:27

be fun Fortunately however as long as we have two

01:29

points on a line we can find it slope Well

01:32

we'll take our old reliable slope formula Why To minus

01:35

y wan over Acts to minus x 1 and plug

01:39

in r point coordinates Your slope is going to be

01:42

fifteen point seven six minus sixteen point two over four

01:47

minus one point five that'll simmer down a negative point

01:51

for for over two point five we'll do the division

01:54

dance and we wind up with a slope of negative

01:58

point one seven six but looks like we can narrow

02:01

it down to options See andy well a and b

02:04

you're going overboard without a life preserver Best of luck

02:07

to you both All right We've checked a slope off

02:09

our to do list but we still need the y

02:11

intercept will to find it We can use the slow

02:14

formula again this time setting x two equal to zero

02:18

will also need one of our points that we know

02:21

are on the line and we'll go with four fifteen

02:23

point seven six since at least there's one whole number

02:27

in there to make our lives A bit easier All

02:29

right now we've got the points for fifteen point seven

02:32

six zero why too And we could do the same

02:35

thing we did earlier to find that why value Remember

02:38

we're setting this whole thing equal to a slope of

02:40

negative point one seven six So negative point one seven

02:45

six equals y two minus fifteen point seven six over

02:48

zero minus four Just negative for we can now multiply

02:51

both sides by negative for to get positive Point seven

02:55

oh for equals y two minus fifteen point seven six

03:00

and finally add fifteen point seven six to both sides

03:03

and why two comes out to be sixteen point four

03:06

six four Well we only have two round that off

03:09

and we've got a perfect match for option d Why

03:12

equals negative point One seven six x plus sixteen point

03:17

four six not a bad exercise Speaking of which we

03:20

could use some exercise we'd love to fit that pair

03:23

of skinny jeans we wore back in high school No

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