Practicing Success
If a2 + b2 = 25, x2 + y2 = 17, ax + by = 8, then find ay - bx |
17 18 19 20 |
19 |
Here note the result : If ax + by = m, and ay - bx = n then (a2 + b2)(x2 + y2) = m2 + n2 Therefore, using this result ⇒ (25) (17) = 82 + n2 ⇒ (25 × 17) - 64 = n2 ⇒ n2 =425 - 64 = 361 ⇒ n = \(\sqrt {361}\) = 19 |