If the sum of the zeroes of 5x²+(p+q+r)x+pqr is zero . . .

Question : If the sum of the zeroes of 5x²+(p+q+r)x+pqr is zero, then find p³+q³+r³.

Doubt by Suraj

Solution : 

5x²+(p+q+r)x+pqr
Here
a=5
b=p+q+r
c=pqr

α+β=-b/a
α+β=-(p+q+r)/5
But α+β=0 (Given)
0=-(p+q+r)/5
0×5=-(p+q+r)
p+q+r=0

Using Identity
If a+b+c=0 then a³+b³+c³=3abc

Here 
p+q+r=0
So, 
p³+q³+r³ = 3pqr