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Solve by elimination: 18x + 4y = -4 -9x + 8y = -8

1 Answer

5 votes

Answer:

x = 0 , y = - 1

Explanation:

given the 2 equations

18x + 4y = - 4 → (1)

- 9x + 8y = - 8 → (2)

multiplying (2) by 2 and adding the result to (1) will eliminate x

- 18x + 16y = - 16 → (3)

add (1) and (3) term by term to eliminate x

(18x - 18x) + (4y + 16y) = - 4 - 16

0 + 20y = - 20

20y = - 20 ( divide both sides by 20 )

y = - 1

substitute y = - 1 into either of the 2 original equations and solve for x

substituting into (1)

18x + 4(- 1) = - 4

18x - 4 = - 4 ( add 4 to both sides )

18x = 0 ⇒ x = 0

solution is x = 0 , y = - 1

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