First slide

Algebra of complex numbers

Question

$I f x = 3 + i t h e n t h e v a l u e o f x^{3} - 3 x^{2} - 8 x + 15$

Easy

A

$- 15$
B

14
C

$15$
D

12

Solution

$G i v e n x = 3 + i x - 3 = i s q u a r i n g o n b o t h s i d e s {(x - 3)}^{2} = - 1 x^{2} - 6 x + 9 = - 1 x^{2} - 6 x + 10 = 0$
$x^{3} - 3 x^{2} - 8 x - 15 = x (x^{2} - 3 x - 8) + 15 = x (6 x - 10 - 3 x - 8) + 15 = x (3 x - 18) + 15 = 3 x^{2} - 18 x + 15 = 3 (6 x - 10) - 18 x + 15 = - 30 + 15 = - 15$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App