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  • Solve this problem - Complex numbers and quadratic equations - JEE Main-5

Let z_{1}=2+3i and z_{2}=-1-5i then  z_{1}z_{2} equals

  • Option 1)

    13-3i

  • Option 2)

    13-13i

  • Option 3)

    13+3i

  • Option 4)

    13+13i

 

Answers (1)

best_answer

z_{1}z_{2}=\left ( 2+3i \right )\left ( -1-5i \right )=\left \{ \left ( 2 \right )\left ( -1 \right )-\left ( 3 \right )\left ( -5 \right ) \right \}+i\left \{ \left ( 3 \right )\left ( -1 \right )+\left ( 2 \right )\left ( -5 \right ) \right \}

\Rightarrow \: z_{1}z_{2}=13-13i

\therefore Option (B)

 

Multiplication of Complex Numbers -

(a+ib)(c+id)=(ac-bd)+i(bc+ad)

-

 

 


Option 1)

13-3i

This is incorrect

Option 2)

13-13i

This is correct

Option 3)

13+3i

This is incorrect

Option 4)

13+13i

This is incorrect

Posted by

prateek

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