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Solve the following system of equations algebraically please ty

Solve the following system of equations algebraically please ty-example-1
User QuinDa
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1 Answer

7 votes

Eliminating y right away is easiest. Add -3(equation 1) to equation 2, and add 3(equation 3) to equation 2:

-3(2x + y + 3z) + (-3x + 3y - 2z) = -3(3) + (-8)

-6x - 3y - 9z - 3x + 3y - 2z = -9 - 8

-9x - 11z = -17

9x + 11z = 17 [equation 1]

3(5x - y + 5z) + (-3x + 3y - 2z) = 3(13) + (-8)

15x - 3y + 15z - 3x + 3y - 2z = 39 - 8

12x + 13z = 31 [equation 2]

Eliminating x next is easier than eliminating z. Add -4(equation 1) to 3(equation 2):

-4(9x + 11z) + 3(12x + 13z) = -4(17) + 3(31)

-36x - 44z + 36x + 39z = -68 + 93

-5z = 25

z = 25/(-5)

z = -5

Plug this into either of the previous equations and solve for x :

9x + 11z = 17

9x + 11(-5) = 17

9x - 55 = 17

9x = 72

x = 72/9

x = 8

Plug x and z into any of the 3 original equations and solve for y :

2x + y + 3z = 3

2(8) + y + 3(-5) = 3

16 + y - 15 = 3

1 + y = 3

y = 2

User Phil Calvin
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