If z1z2∈C,z21+z22ϵR,z1(z21−3z22)=2 and z2(3z21−z22)=11, then the value of z21+z22 is
A
10
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B
12
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C
5
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D
8
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Solution
The correct option is C 5 We have, z1(z21−3z22)=2 (1) z2(3z21−z22)=11 (2) Multiplying (2) by i and adding it to (1), we get z21−3z22z1+i(3z1z2z2−z32)=2+11i ⇒(z1+iz2)3=2+11i (3) Multiplying (2) by i and subtracting it from (1), we get z31−3z22z1−i(3z21z2−z32)=2−11i ⇒(z1−iz2)3=2−11i (4) Multiplying (3) and (4), we get (z21+z22)3=22−121i2=4+121=125 ⇒z21+z22=5