Question

Which of the following is equivalent to $4-\sqrt{-49}$?

• A. $4+i7$
• B. $4-i7$
• C. $4+\sqrt{7}$
• D. $7$

Answer 1

The correct option is B $4-i7$

$\sqrt{-49}=\sqrt{7\times 7\times -1}=\sqrt{7^2}\times \sqrt{-1}$
$=7i$

Hence, $4-\sqrt{-49}=4-i7$

Hence, (b) is the correct option.