Math HELP!

[Marty]

Due tomorrow morning at 7am!

8x^3 means 8x to the power of 3.

Solve the equation 8x^3 - 1,000 = 0
List answers separated by comma's.


There should be 3 answers, anybody got some help for me!??!?!

[uhpilot]

What's the '^' for?

Is the power assigned directly to the x?

[uhpilot]

8x^3 - 1000 = 0

add 1000 to both sides

8x^3 = 1000

then divide both sides by 8

x^3 = 125

then divide both sides by the power of 3

x = 5

Put 5 in the problem to check.

8(5^3) - 1000 = 0
8(125) - 1000 = 0
1000 - 1000 = 0

I don't know where the 3 answers come though. I am a little rusty.
The answer could have been 5,-5 if the power had been an even number power but with an odd number power it has to be positive.

[hugeredford]

one of the answers is 5 but it's kind of hard to understand the problem w/o parentheses

[hugeredford]

you beat me to it

[uhpilot]

Originally Posted by hugeredford

you beat me to it

sorry

[hugeredford]

like you said I don't see how there can be more than 1 answer

[Marty]

Well here is an example...

4x^3 + 0x = 14x^2
answers
X= 0, 7/2, and -0/2

Another example

18x^3+16x=-36x^2
answers
X=0, -3/6, and -2/3

[Marty]

4x^3 + 0x = 14x^2
answers
X= 0, 7/2, and -0/2

Get everything set to 0
4x^3 - 14x^2 + 0x = 0

Take out an X
X(4x^2 - 14x + 0) = 0

Now use the Quadratic Equation
(-b +/- SquareRoot of (b^2-4ac)) / 2(4)

A = 4
B = -14
C = 0

(14 +/- SquareRoot of (196-4(4)(0)) / 8

Follow Order of Operations
(14 +/- SquareRoot of (196)) / 8

Now follow what it says

14 + root of (196) and divide by 8.
then do minus.
14 - root of (196) and divide by 8.

X was taken out earlier and you set that equal to 0 and your answers are...
X= 0, 7/2, and -0/2


See!!! Simple! LOL Took me 45 minutes AFTER I figured this method out to do 25 problems like it.

[hugeredford]

ah yes the quadratic formula just like in mat 114