Question

3x-7y=21. Need the 3 ordered pairs where #1: x=0, is __ #2: y=0, is __ #3: y=-6, is __.

Answer 1

ok, so for the first one, you would plug in 0( which is x) in the equation.:
3(0)-7y=21
0-7y=21
y=21/-7
y=-3, so first ordered pair would be (0, -7)

for the second one you would plug in0 for y this time, and in the third one you would plug in -6 for why, and solve for x on that too. then you have your three ordered pairs

Answer 2

I am still not getting it so need more help

Answer 3

ok, so lets do the second one

Answer 4

ok i tried but got lost

Answer 5

the second one says y= 0
so we are going to plug in 0 for the y, in the function:
3x-7y=21
so when we plug in 0 for y, the function now says:
3x-7(0)=21
next we multiply 0 times 7, so we get:
3x-0=21, which is basically
3x=21
next, we finaly divide 3 on both sides to get x by itself
x=21/3 which is x =7

Answer 6

so now that we know that x=7 , when y=0, the ordered pair is in the form of (x,y) which in this case, it would be (7, 0). that is your second set of points. did you understand this?

Answer 7

well when i did it it was a little different but it did not look right but had the same answer

Answer 8

for the last one i started with 3x-7(-6)=21

Answer 9

then i had 3x-42=21

Answer 10

ok wait a sec

Answer 11

whats -7 *-6?

Answer 12

don't I replace the y with -6?

Answer 13

yes, but what is -7 times -6. can you hold up for a sec

Answer 14

sure

Answer 15

3x-7(-6)=21 is the correct next step, but what do you get when you multiply negative 7 times negative 6?

Answer 16

you get positive 42

Answer 17

so you should have 3x-42=21

Answer 18

no, its going to be
3x+42=21 because we got positive 42, not negative 42

Answer 19

ok i see

Answer 20

yes
3x+42=21, what do we do next?

Answer 21

get x by itself by using 3

Answer 22

OK WAIT

Answer 23

we still have that 42 there, and we need to get rid of it,
so how do we get rid of that 42:
3x+42=21

Answer 24

3x +42 -42 = 21 +42 - 42

Answer 25

there we go! and what do we get?

Answer 26

3x=21

Answer 27

wait whats 21-42? -21!

Answer 28

huh?

Answer 29

I thought the 42s cancelled each other out

Answer 30

yes, but its not 3x=21 its 3x=-21

Answer 31

ok I don't get it

Answer 32

so this is what you got

3x +42 -42 = 21 +42 - 42

Answer 33

right

Answer 34

why did you add 42 both sides? you were only supposed to subtract 42 on both sides. try it again,

Answer 35

3x +42 -42 = 21- 42 is what you should get

Answer 36

ok i put an extra one in there

Answer 37

exactly so figure it from this:
3x +42 -42 = 21- 42

Answer 38

ok so 3x +42 -42 = 0

Answer 39

21 -42= -21

Answer 40

yes so it should be
3x=-21

Answer 41

so (-21,-6) is the ordered pair

Answer 42

we stil need to find x! we were left with
3x=-21 !
remember we need to get x by itself!

Answer 43

ok so we us 3 on both sides

Answer 44

we divide 3 by both sides

Answer 45

damn this thing hangs up on me a lot. so we should end up with x = 21

Answer 46

whats -21/3?

Answer 47

-7

Answer 48

so x=-7.
gosh, what grade are you in? and math level?

Answer 49

I just started college last year Oct and I graduated in 1969 and had just basic math. I was able to transfer 52 credits from my military career. So I am about a late sophmore or early junior. math is 092 which is pre algebra

Answer 50

college 0.0i learned this in 6th and 7th.

Answer 51

ya I know but I have never had algebra before

Answer 52

and im in 9th. yaaay! i feel so smart!

Answer 53

when i was in high school we did not have algebra and geometry. it did not exist

Answer 54

so when i was in 12th they were just starting it as an elective.

Answer 55

I guess that is why it is so hard for me.

Answer 56

whoa! it really does amaze me how far human intelligence has gone. I cant imagine how advanced our human race will be in he next 40 years

Answer 57

ya i know. i wish there was a way for me to shock the heck out my brain so it would be easier for me to learn

Answer 58

lol, so do i! agh sooo much work!

Answer 59

ya but you understand this. I son't understand any of it. I just started in Jan to learn this junk

Answer 60

ya, this si easy. but im doing precal, and ap microecon, and ap Human Geogarohy, and ap bio