x^3-8=0 solve using an appropriate technique????

Question

kaiz122 · Answer

x^3=2^3

kaiz122 · Answer

to get the value of x, simply find the cube root of booth sides of the equation

anonymous · Answer

so it would be 2 and 8  ?

kaiz122 · Answer

no, $$x^3 =2^3$$
$$\sqrt[3]{x^3}=\sqrt[3]{2^3}$$

what would be x?

anonymous · Answer

2 and -2

kaiz122 · Answer

in finding the cube root,there will only be one answer and it's positive.

anonymous · Answer

well i thought that too and on my test i put 2 and she said i needed another answer????

kaiz122 · Answer

it's positive if the radicand is positive and negative if the radicand is negative

kaiz122 · Answer

i think it's the only answer.

anonymous · Answer

ok thank you very much i will question her today on that issue.

kaiz122 · Answer

sorry, but there are other ways for solving it.

x³ - 8 = 0
(x - 2)(x² + 2x + 4) = 0
(x - 2) = 0
x = 2
x² + 2x + 4 = 0
x = {-2 ± √[2² - 4(1)(4)]}/2(1)
x = {-2 ± √[4 - 16]}/2
x = {-2 ± √-12}/2
x = {-2 ± √[(4)(-3)]}/2
x = {-2 ± 2i√3]}/2
x = -1 ± i√3