x+y+3=0,2x−y+1=0 are the equations of the asymptotes of a hyperbola. If (1,−2) is a point on this hyperbola, then the equation of its conjugate hyperbola is
Given equation of asymptotes x+y=−3‌‌‌⋅⋅⋅⋅⋅⋅⋅(i) and‌‌2x−y=−1‌‌‌⋅⋅⋅⋅⋅⋅⋅(ii) On solving Eqs. (i) and (ii), we get centre of hyperbola i.e.x=‌
−4
3
,y=‌
−5
3
i.e. Centre≡(‌
−4
3
,‌
−5
3
) Also combined equation of asymptotes is(x+y+3)(2x−y+1)=0 ⇒‌‌2x2−y2+xy+7x−2y+3=0‌‌‌⋅⋅⋅⋅⋅⋅⋅(iii) Now, equation of hyperbola is (when equation of asymptotes are known) is (x+y+3)(2x−y+1)+c=0 wherecis constant. ∵ (iii) passes through(1,−2). So,(1−2+3)(2+2+1)+c=0 ⇒‌‌(2×5)+c=0⇒c=−10 ∴ Equation of hyperbola is (x+y+3)(2x−y+1)−10=0 Also, equation of conjugate hyperbola is (as we know that, equation of hyperbola, conjugate hyperbola, and pair of asymptotes are same but only difference in constant term). =2x2+xy−y2+7x−2y+13=0