- #1
edieber
- 12
- 0
how do I solve this one?
y=-2x^3-9x^2-60x
y=-2x^3-9x^2-60x
Muzza said:You're going to have to supply more information about the problem. The actual question would be good.
edieber said:how do I solve this one?
y=-2x^3-9x^2-60x
Perhaps, i am missing something here, but what's all the fuss about?
Muzza said:Most of us are not mindreaders, and don't know what people are really asking when they say "solve" and then post a function.
y=xmarlon said:Sorry, but do you know another way to solve a function ?
i think not...
marlon, the mind-reader
dav2008 said:y=x
solve that function
That answer is only true if y is 0.marlon said:hahaha, please ask a more difficult question...
answer : x = 0
marlon
yes indeed it is...dav2008 said:That answer is only true if y is 0.
HallsofIvy said:"Solving means finding the solutions guys...
wow, what a revealing theory...
marlon"
You still haven't understood what everyone is saying! Yes, "solve" means find the solutions- but to what problem?
The orginal post just said "How do I solve this one? y= 3x<sup>3</sup> -9x<sup>2</sup>- 60x"
That's not a "problem" that's just a statement. You then ASSUMED that the problem was "find all values of x that make y= 0" but that certainly is NOT the only possible problem that could be associated with a function.
matt grime said:marlon, they're having you here: one does not solve functions in the sense you think they mean. One solves equations, ie finds their roots, but functions don't possesses roots in this sense.
What about finding the extrema of the function, and/or sketching it? As HallsOfIvy said, there are quite a few possibilities for the meaning of "solve" in this case.marlon said:When no other specific y-values are given it sure is the ONLY possible problem. Let's stop the vagueness here, please...
regards
marlon
HallsofIvy said:So what you are really telling us is that f(x)= 0 is the kind of problem YOU mostly see and you are making an assumption based on YOUR limited experience. Yes, we could have also jumped to that conclusion but most of us have seen many kinds of problems based on a polynomial. Asking for clarification is NOT "making it more difficult". YOU may be satisfied with "an" answer, whether it is right or wrong, we are not. The only person who can clarify the problem is edieber, the original poster, who apparently hasn't even bothered to read the responses to his/her question.
Manchot said:What about finding the extrema of the function, and/or sketching it? As HallsOfIvy said, there are quite a few possibilities for the meaning of "solve" in this case.
matt grime said:Marlon, you were the person who said that some philosophers were speaking of where they knew not and were misusing mathematics, right? Well, saying solve f(x) for some function is also a misuse of mathematical terms.
Whether or not, in your opinion (as you state it to be), the question was clear doesn't mean that the question was actually correct. There may be some element of playing devil's advocate going on, but it is better to stop people misusing terms than letting them carry on being wrong, surely?
JonF said:Marlon you apparently have no idea what a function is. I see that you have read the formal definition, that is good. But, apparently it’s meaning was lost on you.
A function simply is some transformation on a thing (let’s call it a dependant variable) turning into another thing (let’s call it a dependant variable). The function also has another requirement, when you transform an independent variable you only get one result.
So when you ask me to solve
f(x)=-2x^3-9x^2-60x
With out telling me what you want me to transform that independent variable it into, you aren’t supplying sufficient information.
The “-2x^3-9x^2-60x” part is what the transformation this particular function is. It takes an input, cubes it then, multiplies it by –2. After that it takes that same input squares it and multiplies it by –9. Then it takes the input and multiplies it by –60. And lastly it takes those three values and adds them together. What you wanted to know is when will this process give a result of 0. Another equally valid question is when will this process give a result of 10? Or 20?
Functions are very different from equations. With an equation you are trying to find a solution. Functions are entirely different ideas. With functions you give an input and get an output.
For example the function of your height over time could be: for all 0<t<20: f(t) = t(t-20)^(1/2) where f(t) is in inches and t is in years. It makes no sense to solve this equation for 0. Why would you want to know when you were 0 inches tall? But you might want to find out when (or if) you were going to be 6 feet tall. Which would be 72= t(t-20)^(1/2)
Back to your function. What you wanted to ask is what independent variable will make the function yield a value of 0. I.e. solve f(x)=0
But let’s say you wanted to figure out when the function gave a value of, oh 20. I.e. f(x)=20
Then you would get: 20=-2x^3-9x^2-60x
0=-2x^3-9x^2-60x-20
The equation y=-2x^3-9x^2-60x is a polynomial function in standard form, where the variable x is raised to different powers and multiplied by coefficients. It is a third-degree polynomial, also known as a cubic function, and its graph forms a "U" shape.
To solve this equation, you can use different methods such as factoring, the quadratic formula, or the cubic formula. However, since it is a cubic function, the most efficient way is to use the Rational Root Theorem and synthetic division to find the rational roots of the equation. Then, you can use the remaining quadratic equation to find the other two complex roots.
The solutions, also known as the roots, of the equation y=-2x^3-9x^2-60x are the values of x that make the equation true. In this case, there are three solutions, and they can be real or complex numbers. The solutions can be found by solving the equation or by graphing it and finding the x-intercepts.
To graph this equation, you can use a graphing calculator or manually plot points by choosing values for x and calculating the corresponding values for y. You can also use the factored form of the equation, y=-2x(x+5)(x+6), to identify the x-intercepts and the end behavior of the graph. The graph will be a downward-facing "U" shape, with the x-intercepts at (0, 0), (-5, 0), and (-6, 0).
The equation y=-2x^3-9x^2-60x can be used to model various real-life situations, such as population growth, profit and loss in a business, or the motion of a falling object. It can also be used in engineering to design structures or in physics to study the behavior of systems. In economics, this equation can represent the demand curve for a product or service. It is a versatile equation that can be applied in many fields of study.