Question

anybody know anything about Solving Simultaneous equations By Substitution
I know I'm supposed to pick numbers an d put them into my equation for a graph (in my case
-6 to +6
but I still have 1 question how do I know when I have the right number

Answer 1

no sorry im to blonde :( good luck thoigh

Answer 2

then don't respond...

Answer 3

Hey, Josh, how about posting those simult. eqns.?

Answer 4

Line 1: Y - X = 0
Line 2: Y - 3X - 4

Answer 5

Josh, if you're to solve this system using the subst. method, then please just solve one of the equations for either x or y. I'd do that to the first equation, because it's simpler.
Show me your stuff.

Answer 6

well what ever X is in line 1 Y is the opposite

Answer 7

so prob start on line 2:

Answer 8

You could start with either one! I've suggested starting with the first equation because there's less work involved there.

Your task is to solve the first equation for y.

Here's what I'd do:

Write the equation as it is now:

y-x=0
Add x to both sides:

y - x = 0
+x = +x
-------------

Could you do that?

Answer 9

y=0 but that's not possible

Answer 10

Josh:

Here's what I'd get:

y-x=0
x x
--------
y = x

Done. Be sure you're comfortable with this before we move on.

Answer 11

but if u just got rid of x....

Answer 12

What I did was to move that x from the left side to the right side of the equation. The new version of this equation tells us exactly the same information as does the original one.

"If equals are subtracted from equals, the resulting terms are equal."

For now, please accept the fact that y=x.

Answer 13

OH
I see it

Answer 14

Now we act on the fact that y=x.

In the second equation, y-3x=4 (or at least, I'm assuming that that's what you meant).

We substitute y=x. Then x-3x=4. Can y ou solve that for x? Hint: combine x and =3x first.

Answer 15

How are you doing?

Answer 16

ao x is 2

Answer 17

Josh, we have this equation:

x-3x=4

and we want to solve this equation for x.

Combining x and -3x results in -2x, right?

then -2x=4

Divide both sides of this equation by -2 to obtain a value for x. (It's not 2).

Answer 18

X=2
Y=2

Answer 19

If you and I get different results, it's probably because
your second equation was typed as y-3x-4.

Actually, Josh, that is NOT an equation.

Please go back to the orginal problem and type what you meant in the 2nd line.

Answer 20

Happy to "meet" and work with you, Josh. Unfortunately, I need to get off my computer.
Try posting a similar problem; perhaps someone else can help you apply the same principles to solving this new system of equations. Best of luck to you! MM

Answer 21

y - 3x = 4
y = 3x + 4
now sub 3x + 4 in for y in the other equation
y - x = 0
3x + 4 - x = 0
2x + 4 = 0
2x = -4
x = -2
now sub -2 in for x in either of the equations to find y
y - 3x = 4
y - 3(-2) = 4
y + 6 = 4
y = 4 - 6
y = -2
check...
y - x = 0 y - 3x = 4
-2 - (-2) = 0 -2 - 3(-2) = 4
-2 + 2 = 0 (correct) -2 + 6 = 4
4 = 4 (correct)
your solution is (-2,-2)

Answer 22

ok what about 2x-y=4
y=-x+11

Answer 23

main ly 2x-y=4
and lol

Answer 24

@kelliegirl33

Answer 25

@mjbmanny

Answer 26

y = -x + 11
now sub -x + 11 in for y in the other equation
2x - y = 4
2x - (-x + 11) = 4
2x + x - 11 = 4 --- add 11 to both sides
2x + x = 4 + 11
3x = 15
x = 5
now sub 5 in for x into either of your equations to find y
y = -x + 11
y = -5 + 11
y = 6
check..
2x - y = 4
2(5) - 6 = 4
10 - 6 = 4 (correct)

solution is (5,6)

Answer 27

how did u get x=-11 in line 5
@kelliegirl33

Answer 28

2x - (-x + 11) = 4 --- distribute the - through the parenthesis. If it makes it easier, if you just have a sign, with no number, you can put a 1.
Like this...
2x - 1(-x + 11) = 4 -- now distribute through the parenthesis
2x + x - 11 = 4
Understand ?

Answer 29

no

Answer 30

do you know how to distribute through the parenthesis ?

Answer 31

the distributive property yes

Answer 32

thats all I did.
2x - (-x + 11) = 4
If you distributed the negative sign through the parenthesis, what would you get ?

Answer 33

or write it like this...
2x - 1(-x + 11) = 4

Answer 34

2x + -x -11 =4

Answer 35

negative times a negative is a positive
- * -x = x....not -x

Answer 36

oh right

Answer 37

y= -5+11
y=6?

Answer 38

so that leaves : 2x + x - 11 = 4

any more questions ?

Answer 39

correct?

Answer 40

y = -5 + 11
when you are adding/subtracting different signs, you subtract and take the sign of the bigger number.
y = 6

Answer 41

correct..y = 6

Answer 42

(5,6)

Answer 43

correct

Answer 44

now my probem is
i have to draw the line remember how i said earlier that my grah\ph only goes to -6 to +6

Answer 45

you can always check your answers by subbing them into either/both of you equations. If they come out equal, they are correct

Answer 46

never mind lol it said it was bigger

Answer 47

but what ot should be at it still confusing

Answer 48

what ?

Answer 49

i havr to draw the line still

Answer 50

what equation are you trying to graph ?

Answer 51

both

Answer 52

that's what the point is for

Answer 53

you are trying to graph y - x = 0 and y - 3x = 4 ??

Answer 54

never mind that
2x +Y=-1 ho do i change that without - -1
or should it be - -1

Answer 55

I do not understand what you are trying to do. Are you trying to put it in y = mx + b form ?

Answer 56

equation of the line like y=-3x+8

Answer 57

you want me to show you how to graph y = -3x + 8 ??

Answer 58

NO! omg....
2x+y=-1
i made that into 2x=y- -1 is tha6 correct?

Answer 59

2x + y = -1....why are you changing it to 2x = -y - 1 ? It would be easier to solve for y, rather then x.

Answer 60

...

Answer 61

ur missing the point

Answer 62

2x + y = -1
2x = -y - 1
x = -y/2 - 1/2 or x = -1/2y - 1/2

Answer 63

2x + y = -1 is easier to graph?
no i don't think you can graph that

Answer 64

to graph an equation, you need to put it in y = mx + b form

Answer 65

i know that!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 66

2x + y = -1
y = -2x - 1

y intercept is (0,-1)
x intercept can be found by subbing in 0 for y :
2x + 0 = 1
2x = 1
x = 1/2....x intercept is (1/2,0)

slope is -2

Answer 67

what

Answer 68

2x + y = -1to 2x = y - -1 is that right
yes or no

Answer 69

no
2x + y = -1 ----- subtract y from both sides
2x = -y - 1

Answer 70

what happened to the negative on the 1

Answer 71

it stayed the same...we did not even mess with the -1

Answer 72

yes u did

Answer 73

1 had a negative on it!!!!!!!

Answer 74

2x + y = -1 --- subtract y from both sides
2x + y - y = -y - 1 -- combine like terms
2x = -y - 1

Answer 75

THE NEGATIVE!

Answer 76

on the 1

Answer 77

what about the negative on the 1 ? It is still there.

Answer 78

then how about the sign sitting therei wont nibpick at the space u put in there but
there is no sign between the -y and the -1

Answer 79

there does not have to be a sign.....2x = -y - 1 is correct. But if you want to isolate x, you need to divide everything by 2

Answer 80

it is not supposed to be 2x - y - (-1)
because 2x+ y = -1 ---- subtract y from both sides
2x = -y - 1

Answer 81

do you understand ?

Answer 82

i think so working on a problem

Answer 83

ok....tag me if you need help....that is, if you want to :)

Answer 84

ok i will

Answer 85

@kelliegirl33
2X+ Y = -1
and Y=-3X
take -3X and sub for Y
2X + (-3X) = -1
add -3X
2X+3X= -1
5x =-1
what did i do wrong?

Answer 86

@kelliegirl33

Answer 87

2x + y = -1
y = -3x
sub
2x +(-3x) = -1
2x - 3x = -1
-x = -1
x = 1

Answer 88

you did not have to add -3x. All you had to do was distribute the + through the parenthesis. This gave us 2x - 3x = -1. We then combined like terms. -x = -1. I then multiplied by -1 to make x positive.

Answer 89

oh

Answer 90

understand ?

Answer 91

:o

Answer 92

believe me, when you do enough of these, you will get it

Answer 93

this geometry/ algebra III gene doesn't run in my family

Answer 94

geometry...yuck...I am so not good at geometry. Algebra is ok. It just takes a lot of practice to learn all this. I will probably not even need this in my future. Just learn it to get out of high school.....lol

Answer 95

hate to have to break it to you but this is a crossover of geometery

Answer 96

:)(weak smile)

Answer 97

YES OMG YES!!!!!!!