# Bisection Method Help

• Nov 19th 2008, 03:11 PM
nippy_nz
Bisection Method Help
Hi there,

Im trying to find the real root of the equation 0.8x^3-4.2x^2+12.7=0. It is between -2(x0) and -1(x1). My problem is when i try to put the starting values(x0, x1) back into the equation to get y0 and y1 i get incorrect answers... I am easily able to do an equation such as x^5+2x^2-5=0, but not this... Can any body help me? is there something i should be doing with the decimal numbers multiplying x in the equation?
• Nov 19th 2008, 04:52 PM
mr fantastic
Quote:

Originally Posted by nippy_nz
Hi there,

Im trying to find the real root of the equation 0.8x^3-4.2x^2+12.7=0. It is between -2(x0) and -1(x1). My problem is when i try to put the starting values(x0, x1) back into the equation to get y0 and y1 i get incorrect answers... I am easily able to do an equation such as x^5+2x^2-5=0, but not this... Can any body help me? is there something i should be doing with the decimal numbers multiplying x in the equation?

This question has nothing to do with Probability and Statistics. It will get moved to a more suitable subforum.
• Nov 19th 2008, 05:05 PM
nippy_nz
Apologies, this is what i learn in maths with stats class is all. Where would it more suit? Calc?
• Nov 20th 2008, 02:14 PM
Twig
Hi
I´m not sure I understand what you are asking.
The real root?
If you´re looking for the roots to the polynomial this is solved with
calculators or computers.
And there are three real roots to this equation.
I included a picture of the graph.
• Nov 20th 2008, 02:41 PM
nippy_nz
Thanks anyway but as it happened ive learnt to use the newton raphson method aswell and this problem can easily be solved by newton raphson rather than bisection so ill just use that!