Solve the qubic x^3 - 7x + 6 using Cardano's Method. Express all your

answers as possible irrational numbers (i.e. no decimals!) and show your steps.

Please help---this problem is driving me nuts!

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- Nov 25th 2012, 08:33 PMneedhelp2Cardano's Method
Solve the qubic x^3 - 7x + 6 using Cardano's Method. Express all your

answers as possible irrational numbers (i.e. no decimals!) and show your steps.

Please help---this problem is driving me nuts! - Nov 26th 2012, 05:19 PMzhandeleRe: Cardano's Method
I haven't done this in a while but this may help

Cardano's Method

I'll see if I can work out a step or two to get you started.

It looks like your teacher or textbook already did the first step for you, eliminating the square term by the substitution

y = x + (b/3)a - Nov 27th 2012, 07:25 AMtopsquarkRe: Cardano's Method
I'll add to the number of ways to solve this. See this page. I usually use what's called "Vieta's Substitution." (A bit down the page.) And the trigonometric method (further down the page) has its points as well, though it's a bit more complicated. This is really nice if you need to show how many real roots the cubic has.

-Dan