about origin in positive direction. ‌x→x‌cos‌
Ï€
4
−ysin‌‌
Ï€
4
,x→‌
1
√2
(x−y) ‌y→xsin‌‌
Ï€
4
+y‌cos‌
Ï€
4
,x→‌
1
√2
(x+y) So, equation 49x2+25y2=1225 will transform into ‌
49
2
(x−y)2+‌
25
2
(x+y)2=1225 ⇒‌‌37x2−24xy+37y2=1225 On comparing with px2+qxy+ry2=t p=37,q=−24,r‌=37,t=1225. (p+q+r−15)2‌=(37−24+37−15)2 ‌=(35)2=1225 So, (p+q+r−15)2=t