JEE Main 2019 · 9 April · Evening Shift · Mathematics · Complex Number
Let z ∈ C be such that |z| < 1 . If ω = (5 + 3z)/(5(1 - z)), then:
Let z∈C be such that ∣z∣<1. If ω=5(1−z)5+3z, then:
Options
A5Re(ω)>1
B5Im(ω)<1
C5Re(ω)>4
D4Im(ω)>5
Correct answer
A. 5Re(ω)>1
Step-by-step solution
Given ∣z∣<1 and ω=5(1−z)5+3z
⇒5ω(1−z)=5+3z
⇒5ω−5\omegaz=5+3z
⇒z=3+5ω5ω−5
Using the given condition \left|z\right| = 5\left|\dfrac{\omega - 1}{3 + 5\omega}\right| < 1</p><p><imgsrc="https://cdn−question−pool.getmarks.app/pyq/jeemain/6d93483a−6d23−4e29−a9d9−139fafe1e404−image8.png"style="width:250px;height:160px;"/><br/>⇒ 5\left|\omega - 1\right| < \left|3 + 5\omega\right|</p><p>⇒ 5\left|\omega - 1\right| < 5\left|\omega + \dfrac{3}{5}\right|</p><p>⇒ \left|\omega - 1\right| < \left|\omega - \left(- \dfrac{3}{5}\right)\right|</p><p>Weknowthatthelocusofacomplexnumber{z}_{1}satisfying∣z1−a∣=∣z2−b∣ is the perpendicular bisector of the line segment joining the points a and b.
Hence, the locus of the point ω satisfying \left|\omega - 1\right| = ω−(−53) is the line x=21−53=51