Use Cardano’s algebra method to find the roots of  `x^3+6x^2+9x+4=0` 

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Cardano's method applies to what is called the depressed cubic, which is of the form:

`t^3+pt+q=0`

To get the equation into the depressed cubic, use the transformation `x=t-6/3=t-2` to get:

`(t-2)^3+6(t-2)^2+9(t-2)+4`   expand

`=t^3-6t^2+12t-8`    collect like terms

`+6t^2-24t+24`

`+9t-18+4`

`=t^3-3t+2`

This means that the cubic equation to solve...

(The entire section contains 183 words.)

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