Factorising -x^3 + 5x^2 - 7x

James79

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PLS HELP!!! I cant factorise -x^3+5x^2-7x
 
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PLS HELP!!! I cant factorise -x^3+5x^2-7x
\(\displaystyle \\-x^3+5x^2-7x\\-x(x^2-5x+7)\\-x\left( {x - \left[ {\dfrac{{5 + \sqrt 3 i}}{2}} \right]} \right)\left( {x - \left[ {\dfrac{{5 - \sqrt 3 i}}{2}} \right]} \right)\).
 
PLS HELP!!! I cant factorise -x^3+5x^2-7x
The fundamental theorem of algebra says: any polynomial with real coefficients and of degree n, where n is even, can be factored into n/2 quadratic terms with real coefficients and any polynomial with real coefficients and of degree n, where n is odd, can be factored into (n - 1)/2 quadratic terms with real coefficients plus 1 linear term with real coefficients.

Denis has shown you how to do that in this case.

Any quadratic with real coefficients can be factored into two linear terms with either complex or real coefficients. And pka has shown you how to do that in this case.

Edit: by the way, this problem belongs in beginning algebra, not in advanced math.
 
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-x(x^2 - 5x + 7)

use the quadratic formula for the quadratic equation

Be careful reading, Marvin. There is no equation to solve, in this exercise. (All equations contain an equals sign.)

The request asks only for a factorization, not value(s) of x, so the quadratic formula is not required.

Cheers :cool:
 
Be careful reading, Marvin. There is no equation to solve, in this exercise. (All equations contain an equals sign.)The request asks only for a factorization, not value(s) of x, so the quadratic formula is not required.Cheers :cool:
thanks Quaid
 
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