Question

Solve the system by substitution. Show your work. 4 pts 2) -2x - 3 y = -2 y = 2x + 6

Solve the system by elimination. Show your work. 4 pts

3) -x - 18 y = -3
7x - 9 y = 21
please help

I need this before midnight 12/19/2018

Answer 1

2. x=-2 y= 2

3. x=3 y=0

Explanation:

-2x - 3 y = -2

y = 2x + 6

The first step is to get x and y on the same side

Take the second equation and subtract 2x from each side

-2x+ y = 2x-2x + 6

-2x+y = 6

Multiply this by -1

-1(-2x+y) =-1*6

2x -y =-6

Add this to the first equation to eliminate x

-2x - 3 y = -2

2x -y =-6

--------------------

-4y = -8

Divide by -4

-4y/-4 = -8/-4

y =2

Now we need to find x

y = 2x + 6

Substituting in y=2

2 = 2x+6

Subtract 6 from each side

2-6 = 2x+6-6

-4 = 2x

Divide by 2

-4/2 = 2x/2

-2 =x

3) -x - 18 y = -3

7x - 9 y = 21

We will eliminate by by multiplying the second equation by -2

-2(7x - 9 y) = -2*21

-14x + 18y = -42

Now we will add this to the first equation

-x - 18 y = -3

-14x + 18y = -42

-------------------------

-15x = -45

Divide by -15

-15x/-15 = -45/-15

x =3

We still need to solve for y

-x -18y = -3

Substituting in x =3

-3 -18y = -3

Add 3 to each side

-3+3 -18y =-3+3

-18y =0

Divide by -18

y= 0