Answer: k < 4.
- A k > 4
- B k < 4
- C k = 4
- D all real k
Correct answer: B. k < 4
Explanation: Need D ≥ 0 (k ≤ 5), vertex k < 5, and f(5) = k² − 9k + 20 = (k−4)(k−5) > 0. The intersection is k < 4.
A complex number z = a+ib is plotted as a point (or vector from the origin) on the Argand plane, with the real part along the horizontal axis and the imaginary part along the vertical; its modulus |z| is the vector's length, and its argument θ is the angle from the positive real axis.
Concept context
Complex numbers in a+ib form, modulus, argument, polar form, cube roots of unity, and quadratic equations with complex roots
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