SOLUTION: 1. Solve the system by substitution. A) 3x+4y=11. B) 3x+2y=6 -8x-y=19. 2x+5y=-7 2. Solve the system using the addition method A)11x-5y=10. B)10x-4

Algebra ->  Linear-equations -> SOLUTION: 1. Solve the system by substitution. A) 3x+4y=11. B) 3x+2y=6 -8x-y=19. 2x+5y=-7 2. Solve the system using the addition method A)11x-5y=10. B)10x-4      Log On


   

Question 1157002: 1. Solve the system by substitution.
A) 3x+4y=11. B) 3x+2y=6
-8x-y=19. 2x+5y=-7

2. Solve the system using the addition method
A)11x-5y=10. B)10x-4y=7
13x-7y=2. B)4x-y=-5
I need to show the work and I don't understand how to do them.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
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Solve the system by substitution.
A) 3x+4y=11. B) 3x+2y=6
-8x-y=19. 2x+5y=-7
---------------------------------

B was already explained and the best way could be to multiply first equation by 2, second equation by 3, and substitute for 6x.

A:
system%283x%2B4y=11%2C-8x-y=19%29
First easiest to SOLVE FOR y in second equation.
-y=19%2B8x
y=-8x-19
SUBSTITUTE into other equation.
3x%2B4%28-8x-19%29=11
3x-32x-76=11
-29x=76%2B11
-29x=87
x=-3--------------now use this to solve for y, either equation.

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

1. Solve the system by substitution.
A) 3x+4y=11. B) 3x+2y=6
-8x-y=19. 2x+5y=-7

2. Solve the system using the addition method
A)11x-5y=10. B)10x-4y=7
13x-7y=2. B)4x-y=-5
I need to show the work and I don't understand how to do them.
This is how B) needs to be done:

3x + 2y = 6 ------ eq (i)

2x + 5y = - 7 ---- eq (ii)

x - 3y = 13 ------ Subtracting eq (ii) from eq (i)

x = 13 + 3y ------ eq (iii)

3(13 + 3y) + 2y = 6 ------ Substituting 13 + 3y for x in eq (i)

39 + 9y + 2y = 6

11y = - 33

highlight_green%28matrix%281%2C5%2C+y%2C+%22=%22%2C+%28-+33%29%2F11%2C+%22=%22%2C+-+3%29%29

Now, do you think you can find y?