Question

Solve for x in the following equation
-2x^3 = 128

Answer 1

@navk

Answer 2

First step will be to divide by -2 on both sides of the equation. That will give you

x^3 = -64

Now take the cube root..

Answer 3

divide the cube root by -2?

Answer 4

no divide 128 by -2 to get -64

then find the cube root of -64

Answer 5

\[-64=(-4)^3\]

Answer 6

Overview:

1) divide both sides by -2
2) cube root both sides

Answer 7

so it would be x = -4i since you cube root both sides?

Answer 8

Cube root of -64 is not -4i
the imaginary number 'i' appears mostly in square roots not cube roots

Answer 9

Thats because -4 times -4 times -4 = -64

on the other hand -4i times -4i times -4i = -64i^3 = -64 * i^2 * i = -64 * -1 * i = 64i

So -4i can not be a cube root of -64

Answer 10

x = -4

Answer 11

Yes, there are never imaginary numbers when \(\LARGE\color{blue}{ \bf \sqrt[odd]{something} }\)

Answer 12

No imaginaries.

you know that
\(\large\color{blue}{ \bf -64=(-4)^3 }\) AND \(\large\color{blue}{ \bf x^3=x }\)