PLZ I need help! Solve this system using elimination 9x - 8y = -28 and 3x + 4y = 44.

Question

give your answer as a point:

Answer 1

Elimination means that we multiply the equations by values to the point that a variable is reduced to 0 when we add/subtract them together. Lets look at the two you're given:

9x - 8y = -28

3x + 4y = 44

 

There are two possible ways to use elimination fairly easily: we can either multiply the second equation by -3 and negate the x-variable, or multiply it by 2 and negate the y-variable. Let's multiply by 2 in this case:

 

2(3x + 4y = 44) = 6x + 8y = 88

 

9x - 8y = -28

6x + 8y = 88

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

 

9x + 6x = 15x

8y - 8y = 0

-28 + 88 → 88 - 28 = 60

 

So we now have:

15x + 0 = 60

15x = 60

 

Divide both sides by 15:

x = 4

 

Now that we know x, we can solve for y:

9 * 4 - 8y = -28

36 - 8y = -28

-8y = -64

y = 8

 

Check:

3 * 4 + 4 * 8 = 44

12 + 32 = 44

44 = 44

 

Answer 2

9x - 8y = -28 and 3x + 4y = 44

 

To eliminate x, multiply second equation by -3 and add the two equations.

 

9x - 8y = -28

-9x -12y = -132

 

So -20 y = -160 and y = 8

 

Plug into second equation and solve for x.

3x + 4(8) = 44

3x + 32 = 44

3x = 12

x =4

 

(4,8)