Question

If $x=2+5i$ , then value of the expression $x^3-5x^2+33x-49$ equals

• A. $-20$
• B. $10$
• C. $20$
• D. $-29$

Answer 1

Answer: (A)

Given $x=2+5i$
$\Rightarrow x-2=5i$
$\Rightarrow x^2-4x+29=0$
Now, $x^3-5x^2+33x-49$
$=x\left(x^2-4x+29\right)-1\left(x^2-4x+29\right)-20$
$=-20$