Question

Solve by elimination
7x+7y=-7
-10x-7y=28

Answer 1

x = - 7, y = 6

Explanation:

7x + 7y = - 7 -----> equation 1

- 10x - 7y = 28 -----> equation 2

Add equations 1 & 2,

7x + 7y = - 7

- 10x - 7y = 28

___________

- 3x + 0 = 21

- 3x = 21

x = 21 / - 3

x = - 7

Substitute x = - 7 in equation 1,

7x + 7y = - 7

7y + 7x = - 7

7y + 7 ( - 7 ) = - 7

7y - 49 = - 7

7y = - 7 + 49

7y = 42

y = 42 / 7

y = 6

Answer 2

x = -7

y = 6

Explanation:

7x + 7y = -7 ------------------(I)

-10x - 7y = 28 ----------------(II)

Add both the equation and so y will be eliminated and we can find the value of x

(I) 7x + 7y = -7

(II) -10x - 7y = 28 {Now add}

-3x = 21 {Divide both sides by (-3)}

x = 21/-3

x = -7

Plugin x = -7 in equation (I)

7*(-7) + 7y = -7

-49 + 7y = -7

7y = -7 + 49

7y = 42

y = 42/7

y = 6