Solve the system using elimination. 2x – 2y = –8 x + 2y = –1

Question

Solve the system using elimination.

2x – 2y = –8
x + 2y = –1

Answer 1

Jacqueline,

 

Using elimination means we need to "eliminate" one of the two variables so we can solve for the other.

 

In the case of these two, if I add the two equations together like this:

 

2x - 2y = -8

 

+

 

x + 2y = -1

 

I add all like terms first:

 

3x + 0 = -9  (I get 0 since -2y + 2y = 0); we've "eliminated" the variable y.

 

Then:

 

3x = -9

 

Divide both sides by 3 to get:

 

x = -3

 

Now, to find y, just use this value of x in one of the original equations (I'll use the 2nd):

 

-3 + 2y = -1

 

Add 3 to both sides:

 

2y = 2

 

Divide both sides by 2:

 

y = 1

 

Hope this makes sense!

Answer 2

hi Jacqueline,

 

here you have two eqns..

 

as you see both have 2y terms... but in the first eqn it is -2y, the second one it is +2y 

so when you sum those two enqs 

 

you will get...

2x-2y+x+2y=-8-1

2y's will cancel each other

 

what is left

 

3x=-9 

divide by 3 both sides

you get  x=-3

 

good luck