Equation of tangent at point (1,2) at the ellipse 3x2+4y2=19 is 3x(1)+4y(2)=19 3x+8y=19 This line is also tangent to the parabola y2−kx=0 Substitute the value in the above equation. y2−k(
19−8y
3
)=0 3y2+8ky−19k=0 The equation has equal roots. (8k)2−4(3)(−19k)=0 64k2=−(12×19)k k=