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Solve x + 3y = 9
3x – 3y = -13 (1 point)

User Songs
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1 Answer

3 votes

Answer:

(-1, 10/3)

x = -1

y = 10/3

Explanation:

To solve a system, one of the methods you can use is elimination. To use elimination, you need a variable to have the same coefficient in BOTH equations. Since both equations have "3y", with the same coefficient (3), we can use this method.

We want to eliminate a variable by cancelling it out. Since positive 3y PLUS negative 3y is 0, the variable in eliminated. ADD each of the terms in the equations together.

. x + 3y = 9

+ 3x – 3y = -13

. 4x – 0y = -4 3y - 3y = 0

. 4x = -4 Divide both sides by 4 to isolate 'x'

. x = -1 Solved for the x-coordinate

Since we know one variable, 'x', we can easily find the other, 'y'. Substitute 'x' with -1 in any of the equations. Then, isolate 'x'.

x + 3y = 9

(-1) + 3y = 9

-1 + 1 + 3y = 9 + 1 Add 1 to both sides to cancel out left side.

3y = 9 + 1 Add on the right side (9 + 1 = 10)

3y = 10 Divide both sides by 3 to isolate 'y'

y = 10/3 Solved for the y-coordinate

Put the 'x' and 'y' coordinates together in an ordered pair, which you write as (x, y).

The solution to the system is (-1, 10/3).

User Lukos
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