what is the value of x? x^3=64?

2008-12-13 3:01 pm
after that i put x^3-64=0, after: (x-4)(x^2+4x+16)=0. what should i do after these?
更新1:

after that i put x^3-64=0, after: (x-4)(x^2+4x+16)=0. what should i do after these? and i also know that x=4, but its not the only answer.

回答 (9)

2008-12-13 3:22 pm
✔ 最佳答案
x³ - 64 = 0
(x - 4)(x² + 4x + 16) = 0
(x - 4) = 0
x = 4
(x² + 4x + 16) = 0
x = {-4 ± √[4² - 4(1)(16)]}/2(1)
x = (-4 ± √-48)/2
x = (-4 ± 4√-3)/2
x = -2 ± 2√-3
x = -2 ± 2i√3
So x = 4, -2 - 2i√3, -2 + 2i√3
2008-12-13 3:12 pm
The answers above me are right, the solution is quite clearly 4, hoever, if you INSIST on doing it by taking a factor out:

(x-4)(x^2+4x+16)=0

therefore, one of the two must =0:

x-4=0

x=4

the other one gives you:

x^2 +4x +16=0

Which has no (real) solution, therefore the only value for f(x)=0 is the one we just found above:

x=4
2008-12-13 3:48 pm
x³ - 64 = 0
(x - 4)(x² + 4x + 16) = 0
(x - 4) = 0
x = 4
(x² + 4x + 16) = 0
x = {-4 ± √[4² - 4(1)(16)]}/[2(1)]
x = (-4 ± √-48)/2
x = (-4 ± 4√-3)/2
x = -2 ± 2√-3
x = -2 ± 2i√3

Possible values for x are:
x = 4, -2-2i√3, -2 + 2i√3
參考: College student
2008-12-13 3:16 pm
Well, there is an easy way to find the value of x on x^3=64.
Its simple, just get the cube root of 64 answer we get is x=4

x^3=64
x=sqrt[3]{64}
x=4

to check your answer, just plug in x=4 to x^3=64

4^3=64

64=64 correct..
2008-12-13 3:16 pm
x^3=64
Substitute x=4 ,equation satisfies
x*x*x=64
U can factorise 64 as 2*2*2*2*2*2=4*4*4
Here, x=4
2008-12-13 3:10 pm
(x-4) = 0
x=4

(x^2+4x+16)=0
(x+4)(x+4)=0
x= -4

4^3 = 64
(-4)^3 = -64

therefore x=4
2008-12-13 3:09 pm
x^3 = 64
x = ³√64
x = ³√(4 * 4 * 4)
x = 4
2008-12-13 3:08 pm
wrte down the answer to the question, in case you arent smart enough

x=4 so 4^3=64
2008-12-13 3:06 pm
By inspection , x = 4


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