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TS EAMCET · Maths · Straight Lines

When the coordinate axes are rotated about the origin through an angle \(\frac{\pi}{4}\) in the positive direction, the equation \(a x^2+2 h x y+b y^2=c\) is transformed to \(25 x^2+9 y^2=225\), then \((a+2 h+b-\sqrt{c})^2=\)

  1. A 3
  2. B 1225
  3. C 9
  4. D 225
Verified Solution

Answer & Solution

Correct Answer

(B) 1225

Step-by-step Solution

Detailed explanation

\(c=225\) \(\frac{a+b}{2}+h=25\) \(\frac{a+b}{2}-h=9\) \(\frac{b-a}{2}=0 \Rightarrow a=b\) \(a=17, b=17, h=8\) \((a+2h+b-\sqrt{c})^2 = (17+2(8)+17-\sqrt{225})^2\) \(= (17+16+17-15)^2\) \(= (50-15)^2\) \(= (35)^2 = 1225\)