find all the real cube roots of -0.000216
a) 0.0036
b) -0.06
c) 0.0036 and -0.0036
d) -0.06 and 0.06
multiple choice
Well, it has to be negative, say -a if a is a positive number
because (-a)(-a)(-a) = -a^3
but
a*a*a = +a
so that deletes options a) and c) and d)
which leaves us with b)
try b)
(-.06)(-.06)(-.06) = -.000216
sure enough, b) works
I bet the other two roots are complex conjugates :)