Solving systems of equations using Substitution method and elimination

bobbym · 2011-06-28 07:56:15

Hi zee-f;

#15 is not correct.

zee-f · 2011-06-28 08:33:46

and are the rest correct

bobbym · 2011-06-28 08:36:50

Hi;

#16 is correct.

#17 cannot be right. You did not solve or eliminate a variable.

zee-f · 2011-06-28 08:44:26

thanx bobbym ill try doing the rest over again

bobbym · 2011-06-28 08:53:12

To do elimiation you must multiply one equation so that when you subtract them a variable disappears.

Taking a little break, see you later.

zee-f · 2011-06-28 09:42:48

ok so i tried again i hope i did this right

3-3y=x
x+3y=-6

3x+9y=-18
3-3y=x
x+6y=-19x

6y=-19

y=-19/6

anonimnystefy · 2011-06-28 09:53:58

hi zee-f

it's not correct.the system doesn't have any solutions.you can't just say that 19=19x.

zee-f · 2011-06-28 10:14:09

ammmmmmmmmmmmmmmmmmmm i give up lol joking ill try to do it again

anonimnystefy · 2011-06-28 10:39:14

that's the spirit.just keep on trying and you'll get it.

zee-f · 2011-06-29 03:12:32

ok so i tried to do it again

x=3-3y
x+3y=-6

3-3y=x
x+3y=-6

3x=-5x

x=-5/3

bobbym · 2011-06-29 03:23:37

Hi zee-f;

Whoa! My mistake! Did not see that.

Supposing you added 3y to both sides of the first equation.

You would get:

Or.

Now you see that the left hand side of the two equations is the same. But they equal different things! That is not possible, so no solution.

zee-f · 2011-06-29 03:51:55

oooooooooh ok

bobbym · 2011-06-29 03:55:14

How about if you subtracted the 2 equations?

zee-f · 2011-06-29 03:56:27

what about #14

like did i do it correct
3 + -1x = 2x

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-2x' to each side of the equation.
3 + -1x + -2x = 2x + -2x

Combine like terms: -1x + -2x = -3x
3 + -3x = 2x + -2x

Combine like terms: 2x + -2x = 0
3 + -3x = 0

Add '-3' to each side of the equation.
3 + -3 + -3x = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -3x = 0 + -3
-3x = 0 + -3

Combine like terms: 0 + -3 = -3
-3x = -3

Divide each side by '-3'.
x = 1

Simplifying
x = 1

zee-f · 2011-06-29 03:57:40

it if i subtracted i would get 0+0=0

bobbym · 2011-06-29 04:01:58

Hi;

No that is not right. Lets do it. First put everything on the same side for subtraction.

Now if you subtract both eqautions what do you get?

zee-f · 2011-06-29 04:07:54

x-x=0
3y-3y=0
3--6=9

zee-f · 2011-06-29 04:08:54

or would it be x+3y=9

bobbym · 2011-06-29 04:18:13

First one is right but do it by columns just like with numbers:

3 - (-6) = 9

3y - 3y = 0

x - x = 0

0 + 0 ≠ 9

0 ≠ 9

Zero does not equal nine. There is no soultions.

zee-f · 2011-06-29 04:22:43

thanx alot bobbbym i really am having trouble with math these days hey i was wondering did i do number 14 correct ??

bobbym · 2011-06-29 04:24:54

Hi;

Is this your number 14)?

zee-f · 2011-06-29 04:25:42

yup

bobbym · 2011-06-29 04:28:28

Get the x and y on the left.

Now subtract the first equation from the second.

zee-f · 2011-06-29 04:34:15

Y=2x
X+y=3

y-2x=0
x+y=3

2x+2y=6
y-2x=0

2y=6
Y=3

bobbym · 2011-06-29 04:46:12

Hi;

Nope! Here are the equations again.

Please subtract the first equation from the second by matching up the same type variables. In your last post you added, you want to subtract here.

Math Is Fun Forum

#51 2011-06-28 07:56:15

Re: Solving systems of equations using Substitution method and elimination

#52 2011-06-28 08:33:46

Re: Solving systems of equations using Substitution method and elimination

#53 2011-06-28 08:36:50

Re: Solving systems of equations using Substitution method and elimination

#54 2011-06-28 08:44:26

Re: Solving systems of equations using Substitution method and elimination

#55 2011-06-28 08:53:12

Re: Solving systems of equations using Substitution method and elimination

#56 2011-06-28 09:42:48

Re: Solving systems of equations using Substitution method and elimination

#57 2011-06-28 09:53:58

Re: Solving systems of equations using Substitution method and elimination

#58 2011-06-28 10:14:09

Re: Solving systems of equations using Substitution method and elimination

#59 2011-06-28 10:39:14

Re: Solving systems of equations using Substitution method and elimination

#60 2011-06-29 03:12:32

Re: Solving systems of equations using Substitution method and elimination

#61 2011-06-29 03:23:37

Re: Solving systems of equations using Substitution method and elimination

#62 2011-06-29 03:51:55

Re: Solving systems of equations using Substitution method and elimination

#63 2011-06-29 03:55:14

Re: Solving systems of equations using Substitution method and elimination

#64 2011-06-29 03:56:27

Re: Solving systems of equations using Substitution method and elimination

#65 2011-06-29 03:57:40

Re: Solving systems of equations using Substitution method and elimination

#66 2011-06-29 04:01:58

Re: Solving systems of equations using Substitution method and elimination

#67 2011-06-29 04:07:54

Re: Solving systems of equations using Substitution method and elimination

#68 2011-06-29 04:08:54

Re: Solving systems of equations using Substitution method and elimination

#69 2011-06-29 04:18:13

Re: Solving systems of equations using Substitution method and elimination

#70 2011-06-29 04:22:43

Re: Solving systems of equations using Substitution method and elimination

#71 2011-06-29 04:24:54

Re: Solving systems of equations using Substitution method and elimination

#72 2011-06-29 04:25:42

Re: Solving systems of equations using Substitution method and elimination

#73 2011-06-29 04:28:28

Re: Solving systems of equations using Substitution method and elimination

#74 2011-06-29 04:34:15

Re: Solving systems of equations using Substitution method and elimination

#75 2011-06-29 04:46:12

Re: Solving systems of equations using Substitution method and elimination

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