Monday, August 12, 2013

Identify the roots of the equation: `2x^3 + 12 x^2 - 72x - 432` State the multiplicity of each root. .

`2x^3 + 12 x^2 -72x -432 = 2x^2 (x + 6) - 72 (x + 6)`


`= (2x^2 - 72)(x + 6)`


The roots of an equation, f(x) is 'a' if, f(a) = 0.


Thus, the roots of the current equation can be calculated as:


`2x^2 - 72 = 0`


`2x^2 = 72`


`x^2 = 72/2 = 36`


`x = sqrt(36) = 6 and -6`


And another root is:


x + 6 = 0


or, x = -6


Thus the roots of the equation are 6 and -6 (appears twice). 


The equation can also be written in a simplified as: `2 (x+6)^2 (x-6)`


Since, the root x = -6 appears twice in the equation, the multiplicity of -6 is 2. Similarly, the multiplicity of x = 6 is 1.


Hope this helps. 

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