Solve the system

-4x+8y=20

2x+2y=-30

{x, y} = {-35/3,-10/3}

Step-by-step explanation:

-4x+8y=20; 2x+2-30

System of Linear Equations entered:

[1] - 4x + 8y = 20

[2] 2x + 2y = - 30

Solve by Substitution:

/ / Solve equation [2] for the variable y

[2] 2y = - 2x - 30

[2] y = - x - 15

/ / Plug this in for variable y in equation [1]

[1] - 4x + 8• (-x - 15) = 20

[1] - 12x = 140

/ / Solve equation [1] for the variable x

[1] 12x = - 140

[1] x = - 35/3

/ / By now we know this much:

x = - 35/3

y = - x-15

/ / Use the x value to solve for y

y = - (-35/3) - 15 = - 10/3

Solution:

{x, y} = {-35/3,-10/3}

x = - 13 and y = - 4

Step-by-step explanation:

-4x + 8y = 20 ... eqn 1

2x + 2y = - 30 ... eqn 2

Step 1: Multiply eqn 1 by 2 and eqn 2 by 4

(-4x + 8y = 20) * 2

(2x + 2y = - 30) * 4

we will have

-8x + 16y = 40 ... eqn 3

8x + 4y = - 120 ... eqn 4

Step 2: Add eqn 3 and 4 together

20y = - 80

Step 3: divide all through by 20

y = - 80/20

y = - 4

Step 4: Substitute - 4 for y in eqn 1

-4x + 8 (-4) = 20

-4x - 32 = 20

-4x = 20 + 32

-4x = 52

Step 5: Divide both sides by - 4

x = 52/-4

x = - 13