Solve the System: Fractions and Integers in x/2 + y = 3 and x + 2y = 6

System of Equations with Dependent Lines

x2+y=3 \frac{x}{2}+y=3

x+2y=6 x+2y=6

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:04 Let's multiply one of the equations by 2, so we can subtract between them
00:17 Now let's subtract between the equations
00:21 Let's reduce what we can
00:29 There are infinite solutions
00:36 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

x2+y=3 \frac{x}{2}+y=3

x+2y=6 x+2y=6

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Solve the first equation for x x .
  • Step 2: Substitute this expression for x x into the second equation.
  • Step 3: Analyze the resulting equation for y y .
  • Step 4: Determine the relationship between the two equations.

Now, let's work through each step:
Step 1: Starting with the first equation x2+y=3 \frac{x}{2} + y = 3 , we solve for x x by isolating it:
Subtract y y from both sides:
x2=3y \frac{x}{2} = 3 - y
Multiply both sides by 2 to solve for x x :
x=2(3y)=62y x = 2(3 - y) = 6 - 2y

Step 2: Substitute x=62y x = 6 - 2y into the second equation x+2y=6 x + 2y = 6 :
(62y)+2y=6 (6 - 2y) + 2y = 6
Simplify:
6=6 6 = 6

Step 3: The equation 6=6 6 = 6 is always true, indicating there is no contradiction and hence infinitely many solutions when both conditions arise from manipulating consistent equations.

Step 4: Since manipulating these equations leads us to an identity, they are dependent; both equations are forms of the same linear equation x2+y=3 \frac{x}{2} + y = 3 . Each point on this line satisfies both equations, confirming infinite solutions.

Therefore, the solution to the system of equations is infinite solutions.

3

Final Answer

Infinite solutions

Key Points to Remember

Essential concepts to master this topic
  • Substitution Method: Solve one equation for a variable, then substitute
  • Identity Check: When you get 6 = 6, the equations are dependent
  • Verification: Graph both lines to confirm they are identical ✓

Common Mistakes

Avoid these frequent errors
  • Assuming one solution when getting an identity
    Don't think 6 = 6 means x = 6 and y = 6! This identity means the equations represent the same line. Always recognize that a true statement like 6 = 6 indicates infinite solutions, not specific values.

Practice Quiz

Test your knowledge with interactive questions

\( \begin{cases} x+y=8 \\ x-y=6 \end{cases} \)

FAQ

Everything you need to know about this question

What does it mean when I get 6 = 6 after substitution?

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When you get a true statement like 6 = 6, it means both equations represent the same line! Every point on that line satisfies both equations, so there are infinite solutions.

How is this different from getting 0 = 5 or something impossible?

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Great question! When you get something impossible like 0 = 5, the lines are parallel with no solutions. But 6 = 6 is always true, meaning the lines are identical with infinite solutions.

Can I write the infinite solutions in a specific way?

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Yes! You can express the solution as parametric equations. From x=62y x = 6 - 2y , you can write: x = 6 - 2t, y = t, where t is any real number.

How do I verify that there are really infinite solutions?

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Pick any value for y, then calculate x using x=62y x = 6 - 2y . Check that this (x,y) pair satisfies both original equations. Try multiple values to confirm!

Why did multiplying the first equation by 2 give me the second equation?

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Multiplying x2+y=3 \frac{x}{2} + y = 3 by 2 gives x+2y=6 x + 2y = 6 - exactly the second equation! This proves they're the same line written differently.

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