Question

7x+3y=21

Answer 1

im stumped. dont understand how to solve this. this is suppose to be a absolute value equation. plz help me.

Answer 2

There are infinitely many solutions because you have two variables and one equation. You can't solve this.

Answer 3

is there a way to at less write out the problem?
becuz i have tried two different solutions n not sure which one comes close. even though there is not solution

Answer 4

i have tried \[7x/21 +3y/21=21/21=3x+7y\]

Answer 5

\[y=\frac{-7x}{3}+7\]

Answer 6

But what's the goal?

Answer 7

i also tried 7x+3y=21
3y=7x+21
7x/3+21/3

Answer 8

to making y=7/3x+21

Answer 9

the goal ia to find the value of "wat letter? i have no idea."

Answer 10

There's not one value, there are infinity many. 7x+3y=21 describes a line with infinity many points on it. One of those points is (0,7), (3,0) is another for example.

Answer 11

\[ur answer of y=7/3+7 how do u work the problem?\]

Answer 12

so wat ur saying is this answer is just not on one line? its on both a horozontal line n a vertical line?

Answer 13

No, that's not what I said.

Answer 14

I said this:
\[y=\frac{-7x}{3}+7\]
but there's still an x there.

Answer 15

i understand. im just not understanding how t work the problem.

Answer 16

wit two letters im confussed.

Answer 17

so, do i work the problem as such; y=-7/3+1/7 and cancel out the 7's

Answer 18

this problem makes to sense.

Answer 19

I have a hard time understanding you, because the way I see it there's nothing you can do about 7x+3y=21. It's not a problem, you can't solve it.

Answer 20

ok. sorry. i didnt understand. there is no way to solve this problem. i got it now. thx u.

Answer 21

would u like to help me wit another one?

Answer 22

sure

Answer 23

my next problem is

Answer 24

\[2/5(x-6)\ge x-1\]

Answer 25

ok, first thing we need to do is get all the x's on the left side.

Answer 26

To do this we substract x from both sides like this:\[2/5(x-6)-x\ge x-1-x
\]
\[2/5(x-6)-x\ge -1\]
right?

Answer 27

ok

Answer 28

im following u

Answer 29

What's the next thing we should do?

Answer 30

subtract the like terms?

Answer 31

im not sure.

Answer 32

We want to get only one x, now we have two, but we can't subtract them yet because of the (x-6).

Answer 33

So how should we get rid of that?

Answer 34

we multi 2/5 by x-6

Answer 35

right, go ahead.

Answer 36

there is my problem. how do i multi 2/5 by x-6?

Answer 37

is it 2/5 (x)(-6)?

Answer 38

or do i find the lcd?

Answer 39

of 2/5

Answer 40

which would be 10

Answer 41

no, it's a lot easier, you multiply x by 2/5 and -6 by 2/5

Answer 42

like this:
\[2/5x-6(2/5)-x\ge -1\]

Answer 43

\[(2/5)x-6(2/5)-x\ge -1\]
that is.

Answer 44

Now we can subtract the x, so what's (2/5)x-x?

Answer 45

ok.

Answer 46

\[2/5x-6(2/5)-x \ge -1\]

Answer 47

2/5x-6(2/5)-x
-x +x=

Answer 48

so far am i right?

Answer 49

I'm not sure what you mean by your last post.

Answer 50

is my work right so far? subtracting the x's

Answer 51

2/5x-6(2/5)-x
-x +x=

I meant that post, sorry.

Answer 52

You mean you move the -x to the left? That would be a good idea.

Answer 53

thxs. sorry tom, but i truly do not know wat im doing. this math is very hard to me.

Answer 54

ok, so i subtracted the x's

Answer 55

that leaves me wit

Answer 56

\[2/5-6(2/5)\ge -1\]

Answer 57

No, I'm sorry, let me show you:
\[(2/5)x-6(2/5)-x \ge -1\]
\[(2/5)x-x-6(2/5) \ge -1\]
\[(2/5-1)x-6(2/5) \ge -1\]
\[-(3/5)x-6(2/5) \ge -1\]

Answer 58

i dont understand. im trying to understand, but dont know how u got -1 inside the prenthesis

Answer 59

is it +x-x= -1?

Answer 60

If you multiply (2/5-1) by x, the same way as we did before, multiplying 2/5 by x and then -1 by x you end with (2/5)x-x, so it works.

Answer 61

If you like generalizations: a*(b+c)=a*b+a*c

In this case a=x, b=(2/5) and c=-1

Answer 62

ok, that helps somewhat. now, i multi -1 by 3/5 and -6 by 2/5, correct

Answer 63

right

Answer 64

ok, i guess were looking at

Answer 65

I should be going, so let me just finish this:
\[-(3/5)x-6(2/5) \ge -1\]

\[-(3/5)x-(12/5) \ge -1\]
adding (12/5) on both sides
\[-(3/5)x \ge -1+(12/5)\]
dividing both sides by 3/5
\[-x \ge -(5/3)+(12/3)\]
Now perhaps the hardest step, dividing by -1, when you do this the inequality sign changes sides like this:
\[x \le (5/3)-(12/3)\]
The inequality sign always changes when you divide by a negative number.

Answer 66

wow! i was just typing that

Answer 67

I hope you understand it a bit better, see you.

Answer 68

a little. or at least up til the -(3/5)x-(12/5)

Answer 69

now im lost again

Answer 70

im not understanding the addition part an than the division part

Answer 71

i dont know how u came up wit moving everything around

Answer 72

tom i apologize, but my professor didnt even go over these problems. he didnt even slightly touch on them. im feel as if im a poor student or either he's a really horrible teacher. so plz forgive me.