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  • Help me solve this - Complex numbers and quadratic equations - JEE Main-7

If \left ( 1+i \right )\left ( a+ib \right )= 5-i then a+b equals

  • Option 1)

    -3

  • Option 2)

    -2

  • Option 3)

    -1

  • Option 4)

    0

 

Answers (1)

best_answer

\left ( 1+i \right )\left ( a+ib \right )=\left ( 1\times a-1\times b \right )+i\left ( 1\times a+1\times b\right )

\Rightarrow \: \left ( 1+i \right )\left ( a+ib \right )=\left ( a-b \right )+i\left ( a+b \right )

and it is given \left ( 1+i \right )\left ( a+ib \right )=5-i

\Rightarrow \left ( a-b \right )+i\left ( a+b \right )=5-i

So, a - b =5 and a + b =-1

\therefore Option (C)

 

Multiplication of Complex Numbers -

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

-

 

 


Option 1)

-3

This is incorrect

Option 2)

-2

This is incorrect

Option 3)

-1

This is correct

Option 4)

0

This is incorrect

Posted by

Aadil

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