Since α and β are the roots of the equation ax2+bx+c=0, then,
α+β=−ba
And,
αβ=ca
If the roots of any equation is 2α and 2β, then,
(x−2α)(x−2β)=0
x2−2βx−2αx+4αβ=0
x2−2x(α+β)+4αβ=0
x2−2x(−ba)+4(ca)=0
ax2+2bx+4c=0
Therefore, the required equation is ax2+2bx+4c=0.