Question

how do you find the zeros of the function f(x) = 2x^3 – 9x + 3.

Answer 1

have u tried Ruffini's (synthetic division)

Answer 2

newton's method?

Answer 3

no. can you explain how to use it for this problem?

Answer 4

Newton's method doesn't work unless you're a computer or a 17-th century person with too much time. There must be another way!

Answer 5

show me another way then, please?

Answer 6

http://en.wikipedia.org/wiki/Newton's_method#See_also

Answer 7

that's not very helpful.

Answer 8

\[x(9-2x^2)=3\]
Trial and error also works...

Answer 9

Actually, we could find a good approximation, and then use Newton's method.

Answer 10

x=2 is just a bit too small, let's start there.

Answer 11

OK- Newton's method:\[x_1=x_0-\frac{f'(x_0)}{f(x_0)}\] Repeat

Think triangles- f'(x0) is the gradient at x_0 if you don't do calc