第2个回答 2011-12-05
y=1+x^2e^y
y'=2xe^y+x^2y'e^y (1-x^2e^y)y'=2xe^y y'=2xe^y/(1-x^2e^y)
y''=2e^y+2xy'e^y+[(x^2e^y)y' ]'
=2e^y+2xy'e^y+(2xy'e^y+x^2y'^2e^y)+x^2e^yy''
(1-x^2e^y)y''=2e^y+xe^y(4y'+xy'^2)
(1-x^2e^y)y''=2e^y+xe^y(8xe^y/(1-x^2e^y)+2x^3e^y/(1-x^2e^y)^2 )
y''=[2e^y+xe^y(8xe^y/(1-x^2e^y)+2x^3e^y/(1-x^2e^y)^2 )]/(1-x^2e^y)