Multiple choice

Match elements of List I with elements in List II. List 1 List 2 A. If the roots of $x^{3}-9x^{2}+26x-k=0$ are positive and in A.P., then $k$ is 1. $56$ B. If the roots of $x^{3}-14x^{2}+kx-64=0$ are positive and in G.P., then $k$ is 2. $25$ C. If the roots of $6x^{3}-kx^{2}+6x-1=0$ are positive and in H.P., then $3k$ is 3. $-3$ D. In the equation $x^{3}-kx+6=0,$ the sum of two roots is $3$, then the value of the third root is 4. $33$ 5. $24$

  1. $A- 5; B- 1; C- 4; D- 3$
  2. $A- 5; B- 1; C- 3; D- 4$
  3. $A- 1; B- 5; C- 4; D- 3$
  4. $A- 3; B- 1; C- 4; D- 5$
Reveal answer Fill a bubble to check yourself
A Correct answer
AI explanation

For A, let the roots be a-d, a, a+d; their sum is 3a = 9, so a = 3. The product is a(a^2-d^2) = 3(9-d^2) = 26, which yields k = 24 (matching 5). For B, let the roots be a/r, a, ar; their product is a^3 = 64, giving a = 4. The sum of roots taken two at a time is a^2/r + ar + a^2 = 16/r + 4r + 16 = k; since a/r + a + ar = 14, we get 4/r + 4r = 10, so 16/r + 4r = 40, meaning k = 56 (matching 1). For C, if roots are in H.P., the roots of the reciprocal equation -x^3 + 6x^2 - kx + 6 = 0 are in A.P.; letting them be a-d, a, a+d gives 3a = 6, so a = 2, and the product a(a^2-d^2) = 2(4-d^2) = 6 yields d^2 = 1. The sum of products two at a time is a^2-d^2 + a^2 + a^2-d^2 = 3a^2 - 2d^2 = 10, thus k = 11 and 3k = 33 (matching 4). For D, if two roots sum to 3, their product is -6 (from the constant term 6 divided by -1); substituting x = 3 into the equation gives 27 - 3k + 6 = 0, yielding k = 11; the product of all roots is -6, so the third root is -6 / 3 = -3 (matching 3). The correct matching is A-5, B-1, C-4, D-3.