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2x + y = 7
5x + y = 9
Solve the system of equations.

User Siler
by
8.9k points

2 Answers

3 votes
2x + y = 7
- Using elimination
5x + y = 9
__________
-3x + 0 = -2
__________

-3x = -2

x = -2/-3

x = 2/3

From 2x + y = 7, substitute, x = 2/3

2*(2/3) + y = 7

4/3 + y = 7,

y = 7 - 4/3

y = (21 - 4)/3 = 17/3

y = 17/3

x = 2/3, and y = 17/3
User Nicolas Othmar
by
8.8k points
6 votes
The first step of solving a system of equations is to solve one equation for a variable. I'll solve the first one for y.

2x + y = 7 Subtract 2x from both sides
y = -2x + 7

Now, plug that y value into the y of the second equation and solve for x.

5x + y = 9 Substitute
5x + (-2x + 7) = 9 Adjust the signs to get rid of parentheses
5x - 2x + 7 = 9 Combine like terms
3x + 7 = 9 Subtract 7 from both sides
3x = 2 Divide both sides by 3
x =
(2)/(3)

Now, plug that into the first equation.

2x + y = 7 Substitute
2(
(2)/(3)) + y = 7 Multiply

(4)/(3) + y = 7 Subtract
(4)/(3) from each side
y = 5
(2)/(3)

The answer to the system of equations is (
(2)/(3), 5
(2)/(3))
.


User George Osterweil
by
8.7k points

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