4x^3 - 10x^2 + 2= 0 What do I do with the cube?  TOPIC_SOLVED

Quadratic equations and inequalities, variation equations, function notation, systems of equations, etc.

4x^3 - 10x^2 + 2= 0 What do I do with the cube?

Postby Nats on Thu Aug 22, 2013 11:06 am

How do you solve these types of quadratics with cubes and squares? please explain and give a few more examples
I did read Factoring quadratics: the weird case, but I didn't find any example that matches the one I'm currently struggling with.


Thank you. Your help is greatly appreciated.
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Re: 4x^3 - 10x^2 + 2= 0 What do I do with the cube?

Postby little_dragon on Thu Aug 22, 2013 11:55 am

Nats wrote:4x^3 - 10x^2 + 2= 0
How do you solve these types of quadratics...?

it's only "quadratic" if it's squares.
this is "cubic" so "solving quadratics" doesn't apply.
1st: divide thru by 2
2nd: graph on ur calculator
3rd: try this lesson: http://www.purplemath.com/modules/solvpoly.htm
:wave:
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Re: 4x^3 - 10x^2 + 2= 0 What do I do with the cube?

Postby Nats on Thu Aug 22, 2013 1:13 pm

thanks for your reply.

I divided through by two
2x^3 -5x^2 -1 = 0

Im still stuck.
how would i solve this without a calculator?

How do you graph something like this? Isn't I need something like y = mx + b

The link returned an error.
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Re: 4x^3 - 10x^2 + 2= 0 What do I do with the cube?  TOPIC_SOLVED

Postby jg.allinsymbols on Thu Aug 22, 2013 8:03 pm

Nats wrote:How do you solve these types of quadratics with cubes and squares? please explain and give a few more examples
I did read Factoring quadratics: the weird case, but I didn't find any example that matches the one I'm currently struggling with.


Thank you. Your help is greatly appreciated.


Solving cubic equations is usually more advanced in scope than Intermediate Algebra. You should look for possible binomial factors as described in the topic of the Rational Roots Theorem.
Actually, you should factor the polynomial first, into 2(x^3-5+1). You would then want to check for potential zeros from { -1/2, -1, 1/2, 1 }. THIS would be better.

Read about and study the Rational Roots Theorem to find better how this works. You need to use at least polynomial division, if not know synthetic division.
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Re: 4x^3 - 10x^2 + 2= 0 What do I do with the cube?

Postby Nats on Mon Aug 26, 2013 11:01 am

thank you
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