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Mathematics 22 Online
smithm29:

solving problems with linear systems

smithm29:

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Vocaloid:

airplane speed - wind = 2460/4 airplane speed + wind = 2460/5 add the equations together and solve for airplane speed

smithm29:

553.5?

Vocaloid:

good

smithm29:

is that the answer?

Vocaloid:

yes

smithm29:

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Vocaloid:

I'm thinking, please be patient...

smithm29:

sorry

Vocaloid:

if we let small van = x and big van = x + 5 then each morning we have 2x + x + 5 = 65 solve for x

smithm29:

x=20?

Vocaloid:

good, so big bus = x + 5 = ?

smithm29:

25

smithm29:

is the answer?

Vocaloid:

read the question again. you tell me.

smithm29:

sorry i just wanna make sure im right bc i make MANY mistakes

Vocaloid:

good, let's keep going

smithm29:

k

smithm29:

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Vocaloid:

x + y has to be less than/equal to 150 (maximum load) the 2000x + 1500y < = 175,000 (maximum letters)

smithm29:

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Vocaloid:

cost has to be <= 200 bratwurst + burgers >= 150

smithm29:

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Vocaloid:

if y = the more expensive tree then y >= x budget needs to be <= 56000

smithm29:

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smithm29:

should we do the cancel out one?

Vocaloid:

yeah, start by subtracting the equations

smithm29:

x=6?

smithm29:

y=19.7?

Vocaloid:

check your math

Vocaloid:

-17x - 12x = ?

smithm29:

-29x

Vocaloid:

good -95 - 50 = ?

smithm29:

-145

Vocaloid:

good so if -29x = -145 x = ?

smithm29:

5

Vocaloid:

good, now we go back 12(5) = 50 - 10y y = ?

smithm29:

-1?

Vocaloid:

good so (5,-1) = your ans

smithm29:

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Vocaloid:

same process, subtract the two equations make sure you are subtracting the x's, then subtracting the whole numbers

smithm29:

-2

Vocaloid:

good, now let's find y 8(-2) = 84 - 20y

smithm29:

5?

Vocaloid:

good, so -2,5 = ans

smithm29:

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Vocaloid:

add the equations together

smithm29:

-1?

Vocaloid:

good, now let's find y 1 = 29 - 14y y = ?

smithm29:

2?

Vocaloid:

good so (-1,2)

smithm29:

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Vocaloid:

add them together and solve for x

smithm29:

4

Vocaloid:

good so 5(4) = 8 + 6y y = ?

smithm29:

2

Vocaloid:

good, so (4,2) = your answer

smithm29:

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smithm29:

do i add or subtract this one?

Vocaloid:

first multiply the second equation by 2 then subtract and solve for y

Vocaloid:

to determine whether to add/subtract the equation, look at what you are trying to eliminate

Vocaloid:

since we are trying to eliminate the x's, and the x's are both positive, we subtract

smithm29:

um i got -10.2

Vocaloid:

so we have: 14x + 11y = 23 14x - 6y = 74

Vocaloid:

subtract 11y - (-6y) = ?

smithm29:

17y

Vocaloid:

good. 23 - 74 = ?

smithm29:

-51

Vocaloid:

good, so if 17y = -51 then y = ?

smithm29:

-3

smithm29:

?

smithm29:

am i right?*

Vocaloid:

yes good

Vocaloid:

now re-subsbtitute to find x

smithm29:

4?

Vocaloid:

good, so (4,-3)

smithm29:

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Vocaloid:

double the first equation and subtract to find y

smithm29:

-4?

smithm29:

nvm i messed up hold on

smithm29:

y=-5?

Vocaloid:

yes, y = -5 is good

smithm29:

sweet

Vocaloid:

6x + 5(-5) = -19 x = ?

smithm29:

1

Vocaloid:

good, so 1,-5

Vocaloid:

how many are left? I need to go to sleep soon

smithm29:

ik same um... 2 more

smithm29:

is that ok?

Vocaloid:

ok

smithm29:

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Vocaloid:

double first equation then subtract to find y

smithm29:

i dont thik this is right

smithm29:

14.6repeated

Vocaloid:

16x - 8y = -16 16x - 5y = -28 subtract the y's, subtract the whole numbers, then solve for y

Vocaloid:

take it slowly

smithm29:

16x-8y=-16 16x-5y=-28 -3y=-44 /(-3) /(-3) y=14.666 what am i doin wrong?

Vocaloid:

-16 - (-28) is not -44

smithm29:

oh i mustve typed it wrong

Vocaloid:

-16 - (-28) = 12

Vocaloid:

so -3y = 12 and y = -4

smithm29:

yeah i got that now lol

smithm29:

ok soo now plug in y right?

Vocaloid:

yep

Vocaloid:

16x-8(-4 )= -16 x = ?

smithm29:

-3?

Vocaloid:

one more time

smithm29:

never mind i did *8 instead of -16

smithm29:

-8*

smithm29:

-3?

Vocaloid:

good so (-3,-4)

smithm29:

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smithm29:

this is the last one

Vocaloid:

multiply the first equation by 7 and the second equation by 2

Vocaloid:

14x + 14y = -56 -26x + 14y = -96 then subtract to find x

smithm29:

x=1?

Vocaloid:

good

Vocaloid:

14(1) + 14y = -56 y = ?

smithm29:

-5?

Vocaloid:

good, so 1,-5

smithm29:

ok thank u so much and gn

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