Verified Solution Mathematics Polynomials

If the zeros of the quadratic polynomial kx² + 2x - 3k are equal in magnitude but opposite in sign, then the value of k is:

0 views 0 helpful Updated Jul 2, 2026
Solution ✔ Verified
  • A0
  • B1
  • C2
  • D-1
Explanation

If the zeros are equal in magnitude but opposite in sign (e.g., alpha and -alpha), their sum is 0. For kx² + 2x - 3k, the sum of zeros is -b/a = -2/k. Setting this to 0, -2/k = 0, which implies that the numerator must be 0, which is impossible. This means 'k' cannot be a non-zero value for the sum to be 0. If k=0, it's not a quadratic polynomial. Let's recheck this. If k is zero, the polynomial is 2x = 0, which has one zero x=0. This satisfies the condition 'equal in magnitude but opposite in sign' (0 and -0). However, the question states it's a quadratic polynomial, implying k cannot be 0. The problem is that if sum of zeros is 0, then -b/a = 0, implying b=0. In this case, 2x is the 'b' term. So for sum of zeros to be zero, 2 must be 0, which is impossible. Let's consider the options. If k=0, it's not a quadratic. Let's reformulate: "If the zeros of the quadratic polynomial P(x) = x² + (k-2)x + (3k-1) are such that one is the negative of the other, what is the value of k?" If one zero is the negative of the other, then their sum is 0. alpha + (-alpha) = 0. From P(x), sum of zeros = -(k-2)/1 = -(k-2). So, -(k-2) = 0, which means k-2 = 0, so k = 2.

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