WBJEE · Maths · Complex Number
If \(z=x\) - iy and \(z^{1 / 3}=p+\) iq \((x, y, p, q \in \mathbb{R})\), then \(\frac{\left(\frac{x}{p}+\frac{y}{q}\right)}{\left(p^2+q^2\right)}\) is equal to
- A 2
- B -1
- C 1
- D \(-2\)
Answer & Solution
Correct Answer
(D) \(-2\)
Step-by-step Solution
Detailed explanation
\(z=p^3-3 p q^2+i\left(3 p^2 q-q^3\right)=x-i y\) \(\begin{aligned} &x=p\left(p^2-3 q^2\right) \\ &y=-q\left(3 p^2-q^2\right) \\ &\therefore \frac{x}{p}+\frac{y}{q}=p^2-3 q^2-3 p^2+q^2=-2\left(p^2+q^2\right) \end{aligned}\)
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