Mathematics 9709 · AS & A Level · Complex numbers

Complex numbers — practice question

(a)[5]

Show all working, and solve the equation $iz^2 + 2z - 3i = 0$, writing your answers in the form $x + iy$, where $x$ and $y$ are exact real numbers.

(b(i))[2]

On an Argand diagram sketch, draw the locus of complex numbers that satisfy $|z| = |z - 4 - 3i|$.

(b(ii))[3]

Determine the complex number shown by the point on the locus for which $|z|$ is smallest. Find its modulus and argument, and give the argument to 2 decimal places.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Apply the quadratic formula, or let $z=x+iy$ and compare the real and imaginary parts.

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