Equation of a common tangent to `x^(2)+y^(2)=16" and "9x^(2)+25y^(2)=225` is :

The lenth of the portion of the common tangent to x^(2)+y^(2)=16 and 9x^(2)+25y^(2)=225 between the two points of contact is

The lenth of the portion of the common tangent to x^(2)+y^(2)=16 and 9x^(2)+25y^(2)=225 between the two points of contact is

A common tangent to 9x^(2) - 16y^(2) = 144 and x^(2) + y^(2) = 9 is

A common tangent to 9x^(2)-16y^(2)=144 and x^(2)+y^(2)=9, is

The equation of the common tangent to x^(2)+y^(2)=8 and y^(2)=16x is

The equation of the common tangent to y^(2)=2 x and x^(2)=16 y is