What is the implicit derivative of #1= (xy+y)^2-e^(xy) #?

1 Answer
Aug 22, 2016

#y'=[y{2y(x+1)-e^(xy)}]/{xe^(xy)-2y(x+1)^2}#,

or,

#y'=[y{2y(x+1)-y^2(x+1)^2+1}]/{xy^2(x+1)^2-x-2y(x+1)^2}#

Explanation:

We rewrite the given eqn. as #1+e^(xy)=y^2(x+1)^2#.

Diff.ing both sides w.r.t. #x#, we get,

#(1+e^(xy))'={y^2(x+1)^2}'#.

#:. 1'+{e^(xy)}'=(y^2){(x+1)^2}'+(x+1)^2(y^2)'#.

#:. 0+{e^(xy)}'=y^2{2(x+1)(x+1)'}+(x+1)^2(2yy')#.

#:. e^(xy)(xy)'=2y^2(x+1)(x'+1')+2yy'(x+1)^2#.

#:. e^(xy){xy'+yx'}=2y^2(x+1)(1+0)+2yy'(x+1)^2#.

#:. (xy'+y)e^(xy)=2y^2(x+1)+2yy'(x+1)^2#

#:. xy'e^(xy)-2yy'(x+1)^2=2y^2(x+1)-ye^(xy)#

#:. y'{xe^(xy)-2y(x+1)^2}=y{2y(x+1)-e^(xy)}#

#:. y'=[y{2y(x+1)-e^(xy)}]/{xe^(xy)-2y(x+1)^2}#

This can further be simplified by replacing #e^(xy)# by #y^2(x+1)^2-1#

#:. y'=[y{2y(x+1)-y^2(x+1)^2+1}]/{xy^2(x+1)^2-x-2y(x+1)^2}#

Enjoy Maths.!