Help with complex numbers

Simplify the expression.

$\sqrt{- 16 x^{4}}$

$square root of 364$

$negative i square root of 364$

$negative square root of 364$

Simplify the expression.

$\frac{2 - i}{3 - 4 i}$

b. $2 space plus space i$

c. $fraction numerator 2 space plus space 5 i over denominator 13 end fraction$

d. $fraction numerator 2 space plus space 5 i over denominator 5 end fraction$

Simplify the expression.

$\frac{5 - i \sqrt{3}}{5 + i \sqrt{3}}$

b. $fraction numerator 14 space minus space i square root of 3 over denominator 11 end fraction$

c. $fraction numerator 8 space minus space i square root of 3 over denominator 17 end fraction$

d. $fraction numerator 11 space minus space 5 i square root of 3 over denominator 14 end fraction$

Simplify the expression.

i15

a. 1

b. -1

c. i

d. -i

Which of the following is equal to 1?

a. i2

b. i16

c. i21

d. i26