Q.
If the origin and the non-real roots of the equation 3z2+3z+λ=0 , ∀λ∈R are the vertices of an equilateral triangle in the argand plane, then 3 times the length of the triangle is
1628
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NTA AbhyasNTA Abhyas 2020Complex Numbers and Quadratic Equations
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Solution:
Let, z1 and z2 are roots of the equation 3z2+3z+λ=0 ⇒z1+z2=−1 and z1z2=3λ
If 0,z1 and z2 form an equilateral triangle, then z12+z22=z1z2 ⇒(z1+z2)2=3z1z2 ⇒(−1)2=3(3λ)⇒λ=1⇒∣z1z2∣=31 ⇒3∣z1∣=1 unit