Solve each system by elimination

Question

1. -3x+4y=12 2x+y=-8

2. 2x+4y=-4 3x+5y=-3? 

 

 

Answer 1

(1)

-3x+4y = 12            -----------------(1)

2x+y = -8 ⇒ y = -2x - 8    ---------(2)

Substitute y = -2x - 8 in equation (1)

(Here we are eliminating y)

-3x+4y = 12 ⇒ -3x+4(-2x - 8) = 12

-3x - 8x - 32 = 12

-11x  = 12 + 32

-11x = 44

x = - 4

Substitute x = - 4 in equation (2)

y = -2x - 8

y = -2(-4) - 8

y = 8 - 8

y = 0

Solution :

x = - 4 , y = 0

Answer 2

(2)

3x+5y = -3          -----------(1)

2x+4y = - 4

2x = - 4 - 4y

x = (- 4 - 4y)/2

x = - 2 - 2y        -------------(2)

Substitute x = - 2 - 2y in equation (1)

(Here we are eliminating x)

3x+5y = -3 ⇒ 3(- 2 - 2y)+5y = -3

-6 - 6y + 5y = -3

y = -6 + 3

y = - 3

Substitute y = - 3 in equation (2)

x = - 2 - 2y ⇒ x = - 2 - 2(-3)

x = - 2 + 6

x = 4

Solution :

x =  4 , y = -3