If the origin is shifted to $(2,3)$ and the axes are rotated through an angle $45^{\circ}$ about that point,…

If the origin is shifted to $(2,3)$ and the axes are rotated through an angle $45^{\circ}$ about that point, then the transformed equation of $2 x^2+2 y^2-8 x-12 y+18=0$ is
  1. $x^2-7 y^2-14 x y-2=0$
  2. $x^2+y^2=4$
  3. $x^2-y^2=4$
  4. $8 x^2-2 y^2=9$

Solution

Given, equation is $ \begin{array}{rlrl} & & 2 x^2+2 y^2-8 x-12 y+18 & =0 \\ \Rightarrow & 2(x-2)^2+2(y-3)^2 & =8 \\ \Rightarrow & (x-2)^2+(y-3)^2 & =4 \end{array} $ After the shifting of origin to $(2,3)$, the transformed equation becomes $x^2+y^2=4$ and after the rotation of axes through an angle $45^{\circ}$ about the point, the transformed equation is $x^2+y^2=4$. Hence, option (b) is correct

Asked in: AP EAMCET 2019 (20 Apr Shift 2)

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