Find zeroes of the polynomial

Asked by SHAMLI RAUT | 10th Jun, 2013, 07:37: PM

Expert Answer:

Let a, b, c be the zeroes of the given polynomial such that a + b = 0 (since two zeroes are equal in magnitude but opposite in sign)
Now, using the relation between coefficients and zeroes, We have:
Sum of zeroes = -(-5)/1 = 5 = a+b+c
This gives c = 5
 
Also, product of zeroes = -80/1
This gives 5ab = -80
ab = -16
-a2 = -16   (Since, a+b=0 => b = -a)
So, a = 4, or -4
Now, when a = 4, b = -4
and when a = -4, b = 4
 
Thus, the roots are 4, -4, 5.

Answered by  | 10th Jun, 2013, 10:01: PM

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