Theory of Equations
Q. For the equation x^3 - 6x^2 + 11x - 6 = 0, what is the product of the roots? (2019)
Solution
The product of the roots of the cubic equation ax^3 + bx^2 + cx + d = 0 is given by -d/a. Here, d = -6 and a = 1, so the product is -(-6)/1 = 6.
Correct Answer: A — 6
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Q. For the equation x^3 - 6x^2 + 11x - 6 = 0, which of the following is a root?
Solution
By substituting x = 2 into the equation, we find that 2 is a root since 2^3 - 6(2^2) + 11(2) - 6 = 0.
Correct Answer: B — 2
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Q. For the polynomial x^3 - 3x^2 + 3x - 1, what is the nature of its roots? (2020)
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A.
All real and distinct
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B.
All real and equal
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C.
One real and two complex
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D.
All complex
Solution
The polynomial can be factored as (x-1)^3, indicating that it has one real root with multiplicity 3, hence all roots are real and equal.
Correct Answer: B — All real and equal
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Q. For the polynomial x^3 - 3x^2 + 3x - 1, which of the following is true about its roots?
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A.
All roots are real
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B.
All roots are complex
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C.
One root is real
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D.
Two roots are real
Solution
The polynomial can be factored as (x - 1)^3, indicating that all roots are real and equal.
Correct Answer: A — All roots are real
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Q. If the roots of the equation x^2 + 2x + 1 = 0 are equal, what is the value of the discriminant?
Solution
The discriminant is given by b^2 - 4ac. Here, b = 2, a = 1, c = 1, so the discriminant is 2^2 - 4*1*1 = 0.
Correct Answer: A — 0
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Q. If the roots of the equation x^2 + 4x + k = 0 are equal, what is the value of k?
Solution
For the roots to be equal, the discriminant must be zero. Thus, 4^2 - 4*1*k = 0 leads to k = 4.
Correct Answer: B — 8
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Q. If the roots of the equation x^2 + 5x + 6 = 0 are a and b, what is the value of ab? (2023)
Solution
The product of the roots ab is given by c/a. Here, c = 6 and a = 1, so ab = 6.
Correct Answer: A — 6
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Q. If the roots of the equation x^2 - 4x + k = 0 are real and distinct, what is the condition for k? (2023)
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A.
k > 4
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B.
k < 4
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C.
k = 4
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D.
k ≤ 4
Solution
The discriminant must be greater than zero for real and distinct roots: (-4)^2 - 4*1*k > 0, which simplifies to 16 - 4k > 0, or k < 4.
Correct Answer: A — k > 4
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Q. The equation x^2 - 7x + 10 = 0 has roots that are:
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A.
1 and 10
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B.
2 and 5
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C.
3 and 4
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D.
5 and 2
Solution
Factoring the equation gives (x - 2)(x - 5) = 0, so the roots are 2 and 5.
Correct Answer: C — 3 and 4
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Q. The roots of the equation x^2 + 3x + k = 0 are -1 and -2. What is the value of k? (2021)
Solution
The sum of the roots is -1 + (-2) = -3, and the product is (-1)(-2) = 2. Thus, k = 2.
Correct Answer: A — 2
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Q. What is the product of the roots of the equation 2x^2 - 8x + 6 = 0?
Solution
The product of the roots of the equation ax^2 + bx + c = 0 is given by c/a. Here, c = 6 and a = 2, so the product is 6/2 = 3.
Correct Answer: A — 3
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Q. What is the value of k if the equation x^2 + kx + 4 = 0 has equal roots? (2022)
Solution
For equal roots, the discriminant must be zero. Thus, k^2 - 4*1*4 = 0, which gives k^2 = 16, so k = ±4.
Correct Answer: A — 4
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