Answer: a 4.
- A a > -4 and b > 4
- B a < -4 and b > 4
- C a > 4 and b > 4
- D a < 4 and b < -4
Correct answer: B. a < -4 and b > 4
Explanation: Both roots > 2: D = a²-4b ≥ 0; f(2) = 4+2a+b > 0; axis of symmetry -a/2 > 2 (so a < -4). With both roots > 2 and f(2) > 0: b > -2a - 4 > 4. So a < -4 and b > 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
Read the full Complex Numbers and Quadratic Equations notes →