View Full Version : Solving for x-cubic function
trivk96
Oct11-11, 07:27 PM
1. The problem statement, all variables and given/known data
x3-8x+5
2. Relevant equations
3. The attempt at a solution
I am stuck here. I tried factoring.
There's no question here.
What are you trying to do / get to ??
trivk96
Oct11-11, 07:33 PM
Sorry... solve for x
You can't solve for x - you don't have an equation.
trivk96
Oct11-11, 07:37 PM
x3-8x+5 is the equation
x3-8x+5 is the equationThis is NOT an equation. An equation ALWAYS has an = in it.
trivk96
Oct11-11, 07:51 PM
This is NOT an equation. An equation ALWAYS has an = in it.
Sorry...x3-8x+5=0
OK, finally an equation.
Your polynomial doesn't have any nice (i.e., rational) roots, so short of using a very complicated formula from about the 16th century, it looks to me like you need to get the root or roots by graphing the function or using some approximation technique.
What is the complete problem description?
trivk96
Oct11-11, 08:08 PM
Sorry about my terrible earlier posts...
The problem asks me to solve x3-8x+5=0 algebraically
heres what i have gotten to so far. Not sure if this will help me:
i made the original equation into x(x-√8)(x+√8)+5=0
gb7nash
Oct11-11, 08:14 PM
Sorry about my terrible earlier posts...
The problem asks me to solve x3-8x+5=0 algebraically
Did you copy the problem correctly? Are you sure it's not x2-8x+5=0? Otherwise, your problem has no answer (other than using the cubic formula).
Are you absolutely sure this is the equation you're supposed to solve?
x3-8x+5=0
Has your teacher shown you a technique for solving cubic equations? If not, you can't be expected to solve this one.
symbolipoint
Oct11-11, 09:39 PM
1. The problem statement, all variables and given/known data
x3-8x+5
2. Relevant equations
3. The attempt at a solution
I am stuck here. I tried factoring.
supposed to be, x3-8x+5=0.
What course are you in? What methods and techniques have you studied so far? Do you know how many and what kind of roots this equation should have?
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