(i)This is quadratic equation x2-6x-4=0
(ii)This is quadratic equation x3-6x2+2x-1=0
(iii)This is quadratic equation 7x=2x2
(v)This is quadratic equation (2x+1)(3x+1)=6(x-1)(x-2)
(vi)This is quadratic equation 3y2=192