PRACTICAL MATHEMATICS 



a 2 6 2 dx 



or 



a* o'- ax 



^. + x y. d y. = o 



2 r)2 /7 / yi 



U \JuvU 



Hence 

 and 



& L ^iJ iJ __ 1 



7i2 A2 */ /v 



Differentiating 2j/ - + , + = 



or 



% 



dy 



= 



= 2ay + 6 



and 



Differentiating 



or 



dx 



dx 2 dy _ 

 ~ + = 



f?1/ ff^tl 



-Z- x y I ( ) = 

 d# cte 2 \dx/ 



or 



Differentiating 



-} =0 



