Question

Solve each system by elimination.

3) 3x + 4y = 12
-3x - y = 6

4) -5x – 6y = 5
-6x + 6y = 6

5) 7x - 4y = 19
10x - 2y = 16

6) 10x - 9y=-13
5x – 3y =-11

Answer 1

3) x = -4 and y = 6

4) x = -1 and y = 0

5) x = 1 and y = -3

6) x = -4 and y = -3

Explanation:

3) Add the equations:

(3x + 4y = 12) + (-3x - y = 6) (eliminate the x)

= 3y = 18

y = 18/3

y = 6

3x + 4(6) = 12

3x = 12 - 24

x = -12/3 = 4

4) Add the equations:

(-5x - 6y = 5) + (-6x + 6y = 6)

-11x = 11

x = -1

-5(-1) -6y = 5

-6y = 5 - 5

y = 0

5) 7x -4y = 19

10x - 2y = 16

Multiply the second equation by -2 to eliminate the y and add both equations.

-2(10x -2y = 16) =

(-20x + 4y = -32) + (7x - 4y = 19)

-13x = -13

x = 1

7(1) - 4y = 19

-4y = 19-7

y = 12/-4

y = 3

6) multiply the second equation by -2 to eliminate the x and then add the equations.

-2(5x - 3y = - 11) =

(-10x + 6y = 22) + (10x - 9y = - 13)

= -3y = 9

y = - 3

10x - 9(-3) = - 13

10x = -13 - 27

x = -40/10

x = -4