99 Percentile Qs Bank for JEE MainMathematicsEllipse
Assertion (A): The image of x^2 25 + y^2 16 =1 in the line x+y=10 is (x-10)^2 16 + (y-10)^2 25 =1 . Reason (R): The image of a curve ' C ' in a line L is the locus of the image of every point of C with respect to the line L . The correct option among the following is:
Options
- A(A) is true, (R) is true and (R) is the correct explanation for (A)
- B(A) is true, (R) is true but (R) is not the correct explanation for (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
A. (A) is true, (R) is true and (R) is the correct explanation for (A)
Step-by-step solution
Given equation of ellipse is x^2 25 + y^2 16 =1 The image of the ellipse in the line x+y-10 will be (x-h)^2 16 + (y-k)^2 25 =1 Centre of original equation is (0,0) and other equation is (h, k) Midpoint is ( h 2 , k 2 ) Then, x+y-10=0 aligned & h 2 + k 2 =10 & h+k=20 aligned Now, Given equation is perpendicular to the line joining the coordinates (0,0) &(h, k) So, k h (-1)=(-1) From (i), h+k=20 aligned & 2 h=20 & h=10 aligned Then, k=10 Equation of ellipse = (x-10)^2 16 + (y-10)^2 25 =1 It is obtained by the image o