If `(x^(2))/((a-1)(a-2))+(y^(2))/(a(a-3))`=1 represents an ellipse then the value of a belongs to

Equation (x^(2))/(r-2) + (y^(2))/(5-r) = 1 represents an ellipse if

The equation (x^(2))/(10-a)+(y^(2))/(4-a)=1 represents an ellipse , if

(x^(2))/(16-k)+(y^(2))/(k-9)=1 represents ellipse if

If the equation (x^(2))/(16 -K) + (y^(2))/(5-K) = 1 represents an ellipse , then

Equation (x^(2))/(k^(2)-3)+(y^(2))/(2k)=1 represents an ellipse with y-axis as the major axis if k in

Given f is increasing, the equation x^(2)/(f(2a))+y^(2)/(f(a^(2)-3))=1 represents an ellipse with X-axis as major axis if

(x-(1)/(2))^(2)+(y+(1)/(2))^(2)=(k^(2)(x+y+1)^(2))/(8) represents an ellipse then k takes value