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Find all zeros of f(x)=2x^3+3x^2-23x-12

 Oct 22, 2015

Best Answer 

 #1
avatar+26402 
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Find all zeros of f(x)=2x^3+3x^2-23x-12

 

\(2x^3+3x^2-23x-12=0\)

 

1. Try all divider of 12: \(\pm 1, ~ \pm 2,~ \pm 3,~ \pm4, ~\pm 6,~\pm12\)

We find \(x_1 = 3\) and \(x_2 = -4\)

 

2. 

\((x-3)(x+4) = x^2+4x-3x-12 = x^2+x-12\)

 

\(2x^3+3x^2-23x-12 : x^2+x-12=2x+1\)

 

\(2x_3+1 = 0\\ 2x_3 = -1\\ x_3 = -\frac{1}{2}\)

 

We have zeros  \(\mathbf{x_1=3 \qquad x_2 = -4 \qquad x_3= -\frac{1}{2}}\)

 

laugh

 Oct 22, 2015
 #1
avatar+26402 
+35
Best Answer

Find all zeros of f(x)=2x^3+3x^2-23x-12

 

\(2x^3+3x^2-23x-12=0\)

 

1. Try all divider of 12: \(\pm 1, ~ \pm 2,~ \pm 3,~ \pm4, ~\pm 6,~\pm12\)

We find \(x_1 = 3\) and \(x_2 = -4\)

 

2. 

\((x-3)(x+4) = x^2+4x-3x-12 = x^2+x-12\)

 

\(2x^3+3x^2-23x-12 : x^2+x-12=2x+1\)

 

\(2x_3+1 = 0\\ 2x_3 = -1\\ x_3 = -\frac{1}{2}\)

 

We have zeros  \(\mathbf{x_1=3 \qquad x_2 = -4 \qquad x_3= -\frac{1}{2}}\)

 

laugh

heureka Oct 22, 2015

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