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About Linear Equations in Two Variables — Class 9 CBSE

Form and graph linear equations in two variables; find solutions as ordered pairs. This topic is part of the CBSE Class 9 mathematics syllabus (chapter: Chapter 4). On this page you can practice 63 questions across three difficulty levels — 22 easy, 20 medium, and 21 hard — each with a visual step-by-step solution, plus a timed 36-question mastery test with a live leaderboard. Worked examples and sample questions from the topic are below.

What you'll learn in Linear Equations in Two Variables

  • Introduction to Linear Equations in Two Variables
  • Understanding Solutions of Linear Equations
  • Graphing Linear Equations
  • Special Cases: Equations of Lines Parallel to Axes
  • Summary, Connections, and Practice

Interactive lesson · about 15 minutes · checkpoint question after every unit

Linear Equations in Two Variables — solved examples for Class 9 CBSE

Example 1easy

Which of the following is a linear equation in two variables?
  1. A)2x + 3y = 5
  2. B)x² + y = 7
  3. C)xy = 4
  4. D)3x = 9

Step-by-step solution

  1. A linear equation in two variables can be written in the form ax + by + c = 0, where a, b, and c are real numbers, and a and b are not both zero.
  2. The degree of each variable (x and y) must be 1. Option A, 2x + 3y = 5 (or 2x + 3y - 5 = 0), fits this definition as both x and y have a degree of 1.
  3. Options B (x² + y = 7) has x with degree 2, option C (xy = 4) has a product of variables making it non-linear, and option D (3x = 9) is a linear equation in only one variable.

Answer: 2x + 3y = 5

Example 2medium

Express the linear equation 3x = 5y - 7 in the standard form ax + by + c = 0 and identify the values of a, b, and c.
  1. A)a=3, b=5, c=7
  2. B)a=3, b=-5, c=7
  3. C)a=3, b=-5, c=-7
  4. D)a=3, b=5, c=-7

Step-by-step solution

  1. The given equation is 3x = 5y - 7.
  2. To express it in the standard form ax + by + c = 0, move all terms to the left-hand side.
  3. Subtract 5y from both sides and add 7 to both sides: 3x - 5y + 7 = 0.
  4. Comparing this with ax + by + c = 0, we get a = 3, b = -5, and c = 7.

Answer: a=3, b=-5, c=7

Example 3hard

The graph of the linear equation (p-1)x + (2p+1)y = 10 passes through the point (2, 2). What is the value of 'p'?
  1. A)-5/3
  2. B)1
  3. C)5/3
  4. D)2

Step-by-step solution

  1. Substitute the coordinates of the point (2, 2) into the given equation (p-1)x + (2p+1)y = 10.
  2. This gives: (p-1)(2) + (2p+1)(2) = 10.
  3. Expand and simplify the equation: 2p - 2 + 4p + 2 = 10, which simplifies to 6p = 10.
  4. Solve for 'p': p = 10/6 = 5/3.

Answer: 5/3

Practice questions on Linear Equations in Two Variables

  1. Q1.easy

    Express the equation 3x = 5y - 8 in the standard form ax + by + c = 0 and identify the value of 'c'.
    1. A)c = 8
    2. B)c = -8
    3. C)c = 3
    4. D)c = -5
    Show answer

    Answer: c = 8

    Hint: Rearrange the terms to bring all of them to one side of the equation, ensuring the constant term is isolated.

  2. Q2.easy

    Which of the following points is a solution to the equation 2x + y = 7?
    1. A)(1, 4)
    2. B)(3, 2)
    3. C)(2, 3)
    4. D)(0, 7)
    Show answer

    Answer: (2, 3)

    Hint: Substitute the x and y values from each option into the equation and check if it satisfies the equality.

  3. Q3.easy

    Which of the following points is a solution to the equation 2x + y = 7?
    1. A)(1, 4)
    2. B)(3, 2)
    3. C)(2, 3)
    4. D)(4, -1)
    Show answer

    Answer: (2, 3)

    Hint: Substitute the x and y values from each option into the equation and check if it satisfies the equality.

  4. Q4.medium

    Which of the following is NOT a solution to the equation 2x + 3y = 12?
    1. A)(3, 2)
    2. B)(0, 4)
    3. C)(6, 0)
    4. D)(1, 3)
    Show answer

    Answer: (1, 3)

    Hint: Substitute the x and y values from each ordered pair into the equation. If the left-hand side equals the right-hand side, then it is a solution.

  5. Q5.medium

    If the point (k, -2) is a solution of the equation 5x + 2y = 16, what is the value of k?
    1. A)4
    2. B)2
    3. C)-4
    4. D)0
    Show answer

    Answer: 4

    Hint: If a point is a solution, its coordinates must satisfy the equation. Substitute the given x and y values into the equation and solve for k.

  6. Q6.medium

    The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement.
    1. A)x + 2y = 0
    2. B)2x = y
    3. C)x = 2y
    4. D)x - y = 2
    Show answer

    Answer: x = 2y

    Hint: Let 'x' be the cost of the notebook and 'y' be the cost of the pen. Translate the word 'twice' into a mathematical relationship between x and y.

  7. Q7.hard

    A linear equation forms a triangle of area 12 square units with the coordinate axes in the second quadrant. If the y-intercept is (0, 6), what is the equation of the line?
    1. A)3x + 2y = 12
    2. B)3x - 2y + 12 = 0
    3. C)2x + 3y = 12
    4. D)x - 2y + 6 = 0
    Show answer

    Answer: 3x - 2y + 12 = 0

    Hint: The area of a triangle formed by a line and the axes is (1/2) × |x-intercept| × |y-intercept|. Use this to find the x-intercept.

  8. Q8.hard

    For the linear equation ax + by + c = 0, if a + b + c = 0, which of the following points must always be a solution to the equation?
    1. A)(1, 1)
    2. B)(0, 0)
    3. C)(1, 0)
    4. D)(0, 1)
    Show answer

    Answer: (1, 1)

    Hint: Try substituting each option's coordinates into the equation and see which one consistently satisfies the given condition.

  9. Q9.hard

    The total cost of 'x' pens and 'y' notebooks is ₹300. If the cost of each notebook is ₹20, and the cost of each pen is ₹10, and a customer buys twice as many notebooks as pens, which of the following can be a possible number of pens bought?
    1. A)4
    2. B)5
    3. C)7
    4. D)6
    Show answer

    Answer: 6

    Hint: First, form a linear equation based on the total cost. Then, use the relationship between the number of pens and notebooks to eliminate one variable.

These are 9 of the 63 questions available for Linear Equations in Two Variables. Start practicing above to unlock visual solutions, AI coaching, and the topic leaderboard — completely free.