solve the system by addition 2x - 4y = 7 and 4x + 2y = 9?

Question

I have my answer as x = 2.5 and y = - .5
I just want to confirm my answer is right
thanks any one!!!

Answer 1

2x - 4y = 7 and 4x + 2y = 9?
2x=7+4y and 4x=9-2y
2(7+4y)=9-2y
14+8y=9-2y
10y=-5
y=-5/10=/1/2=-0.5

2x-4(-0.5)=7
2x+2=7
2x=5
x=5/2=2.5

CHECK:
4(2.5)+2(-0.5)=9
10-1=9
9=9

You're right.

Answer 2

Solve the system by addition 2x - 4y = 7 and 4x + 2y = 9?

(i stack these.. it makes it easier for me to think

2x-4y=7 (start by multiplying the top equation by (-2) so that
4x+2y=9 you can eliminate the x's

you get -4x+8y=-14
and 4x+2y=9

cancel out the x's and combine the two terms (because with elimination you're pretty just adding the terms) you get

8y+2y=-14+9 (simplify and get) 10y=-5 (divide both sides by the y coefficient (in this term 10) and get y=(-5)/10 (or (-.5) like you got =]

now that you have what "y" equals, plug it back into either of the original two equations (I'll use the first one)

2x-4y=7 so 2x - 4(-.5) = 7 which equals 2x +2=7

subtract two from both sides to get x by itself and get

2x=5 divide both sides by 2 and get x = 5/2. which equals 2.5 =] yes your answers were correct =]

Answer 3

2x – 4y = 7 ........[a million] 4x + 2y = 9 ........[2] [2] * 2 8x + 4y = 18 .......[3] [a million] + [3] 10x = 25 x = 5/2 substitute x with 5/2 in [2] 4 * (5/2) + 2y = 9 10 + 2y = 9 2y = -a million y = -a million/2

Answer 4

Double equation 2 and add to equation 1.
Then you have 10x = 25, or x=2.5. Sub in either eqtn to compute y. y looks OK too. Boorah!!

Answer 5

To confirm your answe is correct, just plug in your values of x and y into the first equation, make sure they work.
then plug the same values into your second equation. If both work, you are correct!!!

Answer 6

yup if you use the subtitution property of linear equations by moving the 4y t one side then dividing by and plugging it in on the other equation then you are right.