a^3-4a^2-13a-40 roots are

Question

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Answer 1

Graph this equation!

Descartes law of signs tells you that there is at most 1 positive real root.

The graph will show you that the root is between 7 and 8 and it cannot be rational since the rational roots would be 1,2,4,5,8,10,20, 40 and the negatives of those numbers.

Your calculator will probably get you the root exactly or you can use Horner's method for irrational roots or Newton's method to get the root yourself.