Which of the following is not a quadratic equation? (A) (x + 2)² = 2(x + 3) (B) x² + 3x = (-1)(1 - 3x²) (C) (x + 2)(x - 1) = x² - 2x - 3 (D) x³ - x² + 2x + 1 = (x + 1)³

MathsCBSE Class 10 · Basic · Sample paper, session 2025-26 · 1 mark · MCQ

CBSE Class 10 Mathematics Basic sample paper 2025-26: question 4

From the official CBSE sample question paper for 2025-26, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q4 · 1 mark · MCQQuadratic Equations

Which of the following is not a quadratic equation?

(A) $(x + 2)^{2} = 2 (x + 3)$
(B) $x^{2} + 3 x = (- 1) (1 - 3 x^{2})$
(C) $(x + 2) (x - 1) = x^{2} - 2 x - 3$
(D) $x^{3} - x^{2} + 2 x + 1 = (x + 1)^{3}$

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

Open one hint at a time and try again before the next.

Hint 1

Expand and simplify each equation.

Hint 2

Check which one loses its $x^{2}$ term.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

(A) simplifies to $x^{2} + 2 x - 2 = 0$ , (B) to $2 x^{2} - 3 x - 1 = 0$ and (D) to $4 x^{2} + x = 0$ . All three are quadratic.
(C): $x^{2} + x - 2 = x^{2} - 2 x - 3$ gives $3 x + 1 = 0$ . This is linear, so it is not quadratic. Option (C).
1 mark

Answer: Option (C)

Where the marks are

Simplifies (C) to the linear equation $3 x + 1 = 0$ (1 mark)

Revise the chapter

Chapter: Quadratic Equations (notes, formulas, where marks are lost and every past question)
Topic: Standard Form of a Quadratic Equation

Practise this chapterBoard-style questions from Quadratic Equations, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26 (Basic): every question, by section.

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CBSE Class 10 Mathematics Basic sample paper 2025-26: question 4

Hints

Step-by-step solution

Revise the chapter

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