Solve By Factoring, and Equation of Cubic Function whose graph passes thru

In summary, the conversation is about two pre-cal problems, one involving factoring and the other involving finding an equation of a cubic function. The first problem is solved by putting all the terms on one side to equal 0. The second problem involves finding the values of a, b, c, and d in the equation y = ax^3 + bx^2 + cx + d, given various points and a tangent. After some trial and error, the solution is found to be -2x^2(x-3).
  • #1
rought
34
0

Homework Statement




I am stuck on these two pre-cal problems... can anyone help?

Solve By Factoring: 2x^3 + 2x^2 = 4x + 4

This next one I have no idea how to do

Find an equation of the cubic function whose graph passes through the points (3,0) and (1,4) and is tangent to the x-axis at the origin...
 
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  • #2
rought said:

Homework Statement



Solve By Factoring: 2x^3 + 2x^2 = 4x + 4

Try putting all the terms on one side so that they all equal 0.
 
  • #3
alrite I think I am ok with the first problem, but I'm still stuck on the second one...
 
  • #4
What can you tell from the point (3,0)?

EDIT: And what can you say since the line passes through the origin?
 
  • #5
You need to find a, b, c, and d of y= ax3+ bx2+ cx+ d so that
a) when x= 3, y= 0
b) when x= 1, y= 4
c) when x= 0, y= 0 and y'= 3ax2+ 2b2+ c= 0.

Putting those values in the equation gives you four linear equations for a,b,c, and d.
 
  • #6
Alright, I think i have it...

It is x^2 because there is a tangent on the x-axis at (0,0), and the other zero is (x-3)

Through a bit of trial and error I have come to: -2x^2(x-3) and I am pretty sure that works just fine.


Thanks again everyone who helped you guys are great! :smile:
 

What is factoring and how is it used to solve equations?

Factoring is a method used to break down an equation into smaller, simpler expressions. By finding the common factors of an equation, we can solve for the unknown variable.

What is the difference between linear, quadratic, and cubic functions?

Linear functions have a constant rate of change and can be represented by a straight line. Quadratic functions have a squared variable and create a parabolic shape on a graph. Cubic functions have a cubed variable and create a curved shape on a graph.

How do you determine the equation of a cubic function from a graph?

To determine the equation of a cubic function from a graph, you need to find the x-intercepts (where the graph crosses the x-axis) and use those points to create the factors of the equation. The general form of a cubic function is ax^3 + bx^2 + cx + d. By plugging in the x-intercepts, you can solve for a, b, c, and d to get the specific equation for the given graph.

What are the different methods for solving cubic equations?

The three main methods for solving cubic equations are factoring, using the cubic formula, and using the rational root theorem. Factoring is the most commonly used method for solving cubic equations.

Can a cubic function have more than one x-intercept?

Yes, a cubic function can have up to three x-intercepts. However, it is possible for a cubic function to have only one or no x-intercepts, depending on the shape of the graph and the values of the coefficients in the equation.

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