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Quadratic Equations appeared 26 times across 3 years — 3% of Mathematics. This question is from Nature of Roots.

Year 2026 2025 2024 Total
Questions 11 10 5 26

For 0 < c < b < a, let (a + b - 2c)x² + (b + c - 2a)x + (c + a - 2b) = 0 and α ≠ 1 be one of its root. Then, among the two statements (I) If α in (-1,0), then b cannot be the geometric mean of a and c (II) If α in (0,1), then b may be the geometric mean of a and c

Solution & Explanation

Related Formula
Sum of coefficients = 0 x = 1 is a root.
Core Logic

Given f(x) = (a + b - 2c)x² + (b + c - 2a)x + (c + a - 2b) = 0. Substituting x = 1:

f(1) = a + b - 2c + b + c - 2a + c + a - 2b = 0

Thus, one root is 1. Let the other root be α.

Step 1: Find the other root

Product of roots = (c + a - 2b)/(a + b - 2c). Since one root is 1, we have:

α · 1 = (c + a - 2b)/(a + b - 2c) α = (c + a - 2b)/(a + b - 2c)
Step 2: Analyze Statement (I)

If -1 < α < 0:

-1 < (c + a - 2b)/(a + b - 2c) < 0

This implies b > (a + c)/(2) and b + c < 2a. Therefore, b cannot be the Geometric Mean of a and c. Statement (I) is true.

Step 3: Analyze Statement (II)

If 0 < α < 1:

0 < (c + a - 2b)/(a + b - 2c) < 1

This gives b > c and b < (a + c)/(2). Therefore, b may be the Geometric Mean between a and c. Statement (II) is true.

Pattern Recognition

When coefficients in a quadratic equation are cyclic and sum to 0, one root is always 1. The other root is directly c/a.

Chapter Mix

Class 11 Maths: Quadratic Equations Class 11 Maths: Sequences and Series

Reference Study Guides

More Quadratic Equations Previous-Year Questions — Page 6

Q20 jee_main_2024_31_jan_morning Sign of Quadratic Expressions
Let S be the set of positive integral values of a for which (ax² + 2(a + 1)x + 9a + 4)/(x² - 8x + 32) < 0, x in R. Then, the number of elements in S is:
  • A. 1
  • B. 0
  • C. ∞
  • D. 3

Solution

Core Logic

For the denominator x² - 8x + 32, D = 64 - 128 < 0 and a = 1 > 0. Thus, x² - 8x + 32 > 0 x in R.

Step 1: Constraint on Numerator

Since the denominator is always positive, the numerator must be strictly negative for all x in R.

ax² + 2(a + 1)x + 9a + 4 < 0 x in R

This requires a < 0 and D < 0.

Step 2: Conclusion

Since a must be strictly less than 0, there are no positive integral values of a that satisfy the condition. Hence, S is an empty set. Number of elements is 0.

Chapter Mix

Class 11 Maths: Quadratic Equations

More Quadratic Equations Questions — jee_main_2024_31_jan_morning

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