Proving Cubic Equation Theta & a,b

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Hai, I have a question solving a cubic equation. I have a function
y=ax*x*x+bx*x. I want to get a solution for the value of a and b. From reference, I found that a=(xtan(Theta)-2y)/(x*x*x) and
b=(3y-xtan(Theta))/(x*x)
[Theta] is an angle or tangent of each point x along a cubic curve or function. Could anyone guide me on how to prove this statement mathematically?
TQ
 
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You want to solve for a and b but you didn't provide any conditions on them.
 
agus said:
Hai, I have a question solving a cubic equation. I have a function
y=ax*x*x+bx*x. I want to get a solution for the value of a and b. From reference, I found that a=(xtan(Theta)-2y)/(x*x*x) and
b=(3y-xtan(Theta))/(x*x)
[Theta] is an angle or tangent of each point x along a cubic curve or function. Could anyone guide me on how to prove this statement mathematically?
TQ

It is not at all clear what you want to do. Find values of a and b so that y= ax3+ bx2 has what properties??
 
Well, anyway, from what you are saying, if we can choose values of X, just let X=1, giving Y=a+b. Then use a second value. Tangent of Theta? It might help to find out what that is.
 

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