Question

Evaluate :
$4\sqrt{-4}+5\sqrt{-9}-3\sqrt{-16}$

• A. $24i$
• B. $31i$
• C. $11i$
• D. $21i$

Answer 1

Answer: (C)

$11i$

The equation can be written as

$4(\sqrt{4}\times \sqrt{-1})+5(\sqrt{9}\times \sqrt{-1})-3(\sqrt{16}\times \sqrt{-1})$

We know that $\sqrt{-1}=i$

$\Rightarrow 4(2\times i)+5(3\times i)-3(4\times i)$

$=8i+15i-12i$

$=11i$