Solve using elimination. –9x + y = 20 –9x − 4y = 10 (_____, _____)

Write Equations: Write down the system of equations. –9x + y = 20 –9x − 4y = 10Eliminate Variable: Decide which variable to eliminate. We can eliminate x by adding the two equations together because the coefficients of x are the same (but with the same sign).Add Equations: Add the two equations together to eliminate x. (–9x + y) + (–9x − 4y) = 20 + 10 This simplifies to: –9x + y – 9x – 4y = 30Combine Terms: Combine like terms. –18x + y – 4y = 30 –18x – 3y = 30 This step is incorrect because we should have eliminated x, but we ended up combining terms incorrectly. The correct combination should be y terms, not x terms. We should have: 0x - 3y = 10

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Solve using elimination. $\newline$ $-9x + y = 20$ $\newline$ $-9x - 4y = 10$ $\newline$ (_, _)

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Grade 8

Solve a system of equations using elimination

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Q. Solve using elimination.

\newline

-9x + y = 20

\newline

-9x - 4y = 10

\newline

(_____, _____)

Write Equations: Write down the system of equations. $\newline$ $-9x + y = 20$ $\newline$ $-9x - 4y = 10$
Eliminate Variable: Decide which variable to eliminate. We can eliminate $x$ by adding the two equations together because the coefficients of $x$ are the same (but with the same sign).
Add Equations: Add the two equations together to eliminate $x$ . $\newline$ $(-9x + y) + (-9x - 4y) = 20 + 10$ $\newline$ This simplifies to: $\newline$ $-9x + y - 9x - 4y = 30$
Combine Terms: Combine like terms. $\newline$ $-18x + y - 4y = 30$ $\newline$ $-18x - 3y = 30$ $\newline$ This step is incorrect because we should have eliminated $x$ , but we ended up combining terms incorrectly. The correct combination should be $y$ terms, not $x$ terms. We should have: $\newline$ $0x - 3y = 10$