Solving an equation by the elimination method

[hharris32]

Can anyone please help me with this?
3x+4y=2
6x+8y=4
I am supposed to solve by the elimination method? But I am not sure where to begin, and when I try I continuously get the wrong answer.
Thank you.

 

[Deleted member 4993]

Can anyone please help me with this?
3x+4y=2
6x+8y=4
I am supposed to solve by the elimination method? But I am not sure where to begin, and when I try I continuously get the wrong answer.
Thank you.

Take one of the equations and solve it for 'y' - in terms of 'x'.

Take the above expression for 'y' and introduce it to the second equation and solve.

Example

x - y = 5....................................................(1)
x + y = 9....................................................(2)

fro (1) we get,

y = x - 5....................................................(3)

using (3) in (2)

x + (x - 5) = 9

2x - 5 = 9

2x = 14

x = 7......................................................(4)

using (4) in (7)

y = 7 - 5

y = 2...............................................................................(5)

Now use (4) and (5) into (1) and (2) to check your solution

 

[Denis]

3x+4y=2
6x+8y=4
I am supposed to solve by the elimination method

2nd equation is same as the 1st: 1st is multiplied by 2 :shock:

Why d'heck teacher gives you this when you're still "learning" is beyond me !

 

[mmm4444bot]

Subhotosh showed you the substitution method.

The elimination method is different.

In the elimination method, we first choose which of the two variables we want to eliminate.

Then we multiply one (or both) equations by appropriate numbers so that the coefficients on the variable we want to eliminate are equal in magnitude but opposite in sign.

When the coefficients on our chosen variable are equal and opposite, then they cancel when the two equations are added together.

Denis noted that the second equation is simply the first equation multiplied by 2.

Therefore, if we mutliply the first equation by -2, the coefficients will end up equal and opposite.

-6x - 8y = -4

Now, we add this equation to the second equation.

-6x - 8y = -4
6x + 8y = 4
---------------
0 = 0

When all of the variables are eliminated, and we end up with a true statement (like 0=0), then this indicates that there are an infinite number of solutions.

CLICK HERE for an on-line lesson for the elimination method.

 

[Deleted member 4993]

Re:

Subhotosh showed you the substitution method.

Egad - I am over my quota !! Anyway, I always get tangled up in those names.....