Q.
Let the complex number z be root of the equation 11z10+10iz9+10iz-11=0, then which of the following statement(s) is/are correct?
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a
z2+z+1=3
b
z2−z+1=1
c
z2+z+1=7
d
z2+z+1=8
answer is A.
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Detailed Solution
11z10+10iz9+10iz-11=0 ⇒z911z +10i=11-10iz ⇒z9=11-10iz11z+10i⇒z9=11i+10z11z+10i ⇒11i+10z2-11z+10i2=112-1021-z2 =211-z2 for z<1⇒11i+10z2-11z+10i2>0 ⇒ z9==11i+10z11z+10i>1⇒z9>1 which contradicts with z<1for z>1 we get z9<1 therefore z=1
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