Question

{} = {x|x is a real number and x^2=-1}
True or false? why?

Answer 1

false..
if x a real number (maybe positive, zero or a negative number)
then x^2 must be a postive number and impossible to get a negative number

Answer 2

in quadratic function : y = ax^2+bx+c
for the value the discriminant (D) < 0, its called definite positive
with D=b^2-4ac
so, x^2 = -1 or
x^2 + 1 = 0
D=0^2-4(1)(1) = -4

Answer 3

\[x=\pm i, \qquad \pm i\not\in \mathbb R\]

Answer 4

haha~ true..coz x^2 cannot be -1..thxs a lot..

Answer 5

yepss.. :)