Determine the best method to solve the system of equations. Then solve the system.

5x+7y=-11

5x-3y=19

Guest Mar 6, 2017

#1**+6 **

The fastest method looks like "elimination," where you line the equations up and add straight down.

5x + 7y = -11

5x - 3y = 19

If we added straight down right now, that would give us 10x + 4y = 8, which doesn't help any. We want one of the variables to go away.

Multiply the top equation by negative one all the way through.

(-1)(5x + 7y) = (-1)(-11)

-5x - 7y = 11

Now line up both equations and add straight down:

-5x - 7y = 11

__5x - 3y = 19 __

0 - 10y = 30

-10y = 30

**y = -3**

Plug in y into either one of the equations to find x:

5x - 3(-3) = 19

5x + 9 = 19

5x = 10

**x = 2**

hectictar
Mar 6, 2017

#1**+6 **

Best Answer

The fastest method looks like "elimination," where you line the equations up and add straight down.

5x + 7y = -11

5x - 3y = 19

If we added straight down right now, that would give us 10x + 4y = 8, which doesn't help any. We want one of the variables to go away.

Multiply the top equation by negative one all the way through.

(-1)(5x + 7y) = (-1)(-11)

-5x - 7y = 11

Now line up both equations and add straight down:

-5x - 7y = 11

__5x - 3y = 19 __

0 - 10y = 30

-10y = 30

**y = -3**

Plug in y into either one of the equations to find x:

5x - 3(-3) = 19

5x + 9 = 19

5x = 10

**x = 2**

hectictar
Mar 6, 2017