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If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing G.P., then
  • a)
    b + c = 0
  • b)
    b ∈ (−∞, −3)
  • c)
    One of the roots is 1
  • d)
    One root is smaller than one and one root is more than 1
Correct answer is option 'A,B,C,D'. Can you explain this answer?
Most Upvoted Answer
If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing...
To determine the conditions for the roots of the equation x^3 + bx^2 + cx - 1 = 0 to form an increasing geometric progression (G.P.), we need to analyze the equation and its properties.

Analysis of the Equation:
The equation x^3 + bx^2 + cx - 1 = 0 can be written as:
x^3 + bx^2 + cx = 1

Key Points:
1. Sum of Roots:
The sum of the roots of the equation is given by the coefficient of x^2 with a negative sign, i.e., -b. Therefore, the sum of the roots is -b.

2. Product of Roots:
The product of the roots is given by the constant term, i.e., -1.

Conditions for Roots to Form an Increasing G.P.:
For the roots of the equation to form an increasing G.P., the following conditions must be satisfied:

A. Roots in an Increasing Order:
The roots should be arranged in an increasing order.

B. Common Ratio of the G.P.:
The common ratio (r) of the G.P. can be obtained by dividing the second root by the first root. Let the roots be a, ar, and ar^2. Therefore, the common ratio (r) can be expressed as:
r = (ar)/(a) = ar/a = r^2

C. Sum of Roots in G.P. Form:
The sum of the roots should be equal to the sum of the terms of a G.P. with the first term as a and the common ratio as r. The sum of the terms of a G.P. can be expressed as:
Sum = a(1 - r^n)/(1 - r)
where n is the number of terms in the G.P.

D. Product of Roots in G.P. Form:
The product of the roots should be equal to the product of the terms of a G.P. with the first term as a and the common ratio as r. The product of the terms of a G.P. can be expressed as:
Product = a^n

Combining the Conditions:
To satisfy all the conditions mentioned above, the following equations need to be satisfied simultaneously:

1. Roots in an Increasing Order: No specific equation required.

2. Common Ratio of the G.P.:
r = r^2
This equation implies that r = 0 or r = 1.

3. Sum of Roots in G.P. Form:
Sum = a(1 - r^n)/(1 - r) = -b
This equation relates a, r, and b.

4. Product of Roots in G.P. Form:
Product = a^n = -1
This equation relates a and n.

Based on the above analysis and conditions, we can conclude the following:

A. Roots can be arranged in an increasing order if:
No specific equation required.

B. Possible values for the common ratio (r) are:
r = 0 or r = 1

C. The sum of roots (a(1 - r^n)/(1 - r)) can be equal to -b if:
b, c ∈ (-∞, -3)

D. The product of roots (a^n) can be equal to -1 if:
One of the roots is 1

Therefore, the correct answer is option 'A, B, C, D'.

Note: The above explanation and conditions are applicable for the
Free Test
Community Answer
If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing...
Let the roots of the given equation be a/r, a, ar where a > 0 & r > 1, then
From equation (iii)iii, we get a3 = 1⇒ a = 1
From equation (i), we get
Also, from equation (ii), we get
From equations (iv) & (v), we get
−b = c ⇒ b + c = 0
As
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If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing G.P., thena)b + c = 0b)b ∈ (−∞, −3)c)One of the roots is 1d)One root is smaller than one and one root is more than 1Correct answer is option 'A,B,C,D'. Can you explain this answer?
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If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing G.P., thena)b + c = 0b)b ∈ (−∞, −3)c)One of the roots is 1d)One root is smaller than one and one root is more than 1Correct answer is option 'A,B,C,D'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing G.P., thena)b + c = 0b)b ∈ (−∞, −3)c)One of the roots is 1d)One root is smaller than one and one root is more than 1Correct answer is option 'A,B,C,D'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If the roots of the equation x3 + bx2 + cx − 1 = 0 form an increasing G.P., thena)b + c = 0b)b ∈ (−∞, −3)c)One of the roots is 1d)One root is smaller than one and one root is more than 1Correct answer is option 'A,B,C,D'. Can you explain this answer?.
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