Question

Can someone please check my work? Please? I would really appreciate it...
Question~
Solve the systems using the elimination method.
y = x - 1
y = -x + 7

Answer 1

My Answer~
-2x+y=-1
X+y=7
=
-2x+y=-1 Multiply by 1
X+y=7 multiply by 2
=
2x-1=-x+7
3x-1=7
3x=8
X=8/3
Y=13/3
Final answer~ (8/3, 13,3)

Answer 2

what my teacher said was wrong~
your first equation under Answer doesn't make sense

Answer 3

@phi could you show me what I did wrong? Please?

Answer 4

Is this the problem
y = x - 1
y = -x + 7

?

Answer 5

Yes sir this is the problem I need help with

Answer 6

What is the first step you have been taught to do ?

Answer 7

to Line up the x's above each other, the y's above each other, and the equals signs and the constants above each other.

Answer 8

though you don't have to, it is best to put all equations into standard form
with all the variables on the left side of the = sign

for example
y= x-1
I would add -x to both sides
what do you get ?

Answer 9

can you write -x on both sides ?

Answer 10

so it will look like this?
y=x-x-1-x?
or
y=x-1-x?

Answer 11

almost. you "do the same thing" to each side
you start with
y = x -1
write
-x + y = x - 1 -x
on the right side x -x simplifies to 0 so you get
-x + y = -1

Answer 12

notice in your answer you wrote
My Answer~
-2x+y=-1

that is different from what you should get: -x + y = -1

Answer 13

for the 2nd equation
y = -x + 7

add +x to both sides

Answer 14

I am soooo sorry but I typed it wrong!! it's supposed to be ~
y = 2x - 1
y = -x + 7
NOT
y = x - 1
y = -x + 7
I forgot the 2.... I am very sorry

Answer 15

ok, then you should get
-2x+y= -1
x +y = 7

if you multiply the 2nd equation by 2 (I think that is what you did next) you get

-2x+ y = -1
2x+2y = 14
------------
0 + 3y= 13 add the 2 equations
y= 13/3

and x will be 7-13/3 = 21/3 - 13/3 = 8/3

which is what you got.


you did it correctly, so I am not sure what your teacher does not like

Answer 16

So does it look like I missed a step or something? @phi

Answer 17

No, it looks ok
That is why I asked what the problem was, because if you were solving the wrong problem that would explain your teacher's comment.

Answer 18

although, looking at your answer, you solved it using "substitution" and they wanted you to solve it using "elimination"

Answer 19

ooh ok... would you mind helping me do that?

Answer 20

You start off good, with

My Answer~
-2x+y=-1
X+y=7

then you say
-2x+y=-1 Multiply by 1
X+y=7 multiply by 2

(I would not bother multiplying by 1 in the 1st equation because that does not do anything)

for the 2nd equation, "multiply by 2" means multiply both sides and all terms by 2
you should get
2x+2y=14


and the equations are now

-2x+y= -1
2x+2y= 14

Answer 21

the idea is when you now add the 2 equations the -2x+2x =0 (is "eliminated")

so add the two equations
-2x+y= -1
2x+2y= 14

can you do that ?

Answer 22

@phi I am very sorry but I fell asleep...