Let α and 4β be roots of x2−6x+a=0 and α,3β be the roots of x2−cx+6=0, then α+4β=6 and 4αβ=a α+3β=c and 3αβ=6. We get αβ=2⇒a=8 So the first equation is x2−6x+8=0⇒x=2,4 If α=2 and 4β=4 then 3β=3 If α=4 and 4β=2, then 3β=3/2 (non-integer) ∴ common root is x=2.