If asecα+btanα=1 and a2sec2α−b2tan2α=5 then 4a2−9b2  =

asecα+btanα=1   →(1)  (asecα+btanα)(asecα−btanα)=5 1(asecα−btanα)=5  → (2) (1)+(2) ⇒secα=3a   (1)-(2) ⇒tanα=−2b sec2α−tan2α=1⇒4a2−9b2=−a2b2