Question

Which of the following is an empty set

• A.
• B.
• C.
• D.

Answer 1

Answer: (B), (D)

The correct options are
B

D

Since $x^2$ + 25 = 0, gives $x^2$ = -25

⇒ x = ± 5i

∴ x is not real but x is real (given)

Similarly, for $x^2$ = -36
x = ± 6i

∴ No value of x is possible.
So, options B and D are null sets.