a2 + b2 = 41 x2 + y2 = 16 ax + by = 20 Find ay - bx:

13 17 16 15

16

Formula → (a2 + b2) (x2 + y2) = (ax + by)2 + (ay - bx)2 Let ay - bx = t 41 × 16 = (20)2 + t2 656 = 400 + t2 t = \(\sqrt {256}\) = 16