The structure of $IF_7$ is $......$ .

If $A(1,2,3), B(3,7,-2), C(6,7,7)$ and $D(-1,0,-1)$ are points in a plane, then the vector equation of the line passing through the centroids of $\triangle ABD$ and $\triangle ACD$ is

The major product of the following reaction is

The product is:

Which one of the following is not correct?

The condition that the roots of $x^3-b x^2+c x-d=0$ are in geometric progression is