4-1.Complex numbers
easy

The values of $x$ and $y$ for which the numbers $3 + i{x^2}y$ and ${x^2} + y + 4i$ are conjugate complex can be

A

$( - 2, - 1)$or $(2, - 1)$

B

$( - 1,{\rm{ }}2)$or $( - 2,{\rm{ }}1)$

C

$(1,\,2)$or $( - 1, - 2)$

D

None of these

Solution

(a) According to condition, $3 – i{x^2}y = {x^2} + y + 4i$
$⇒$  ${x^2} + y = 3$and ${x^2}y = – 4$ $⇒$  $x = \pm 2,y = – 1$
$⇒$  $(x,y) = (2, – 1)$or $( – 2, – 1)$

Standard 11
Mathematics

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