e？ =? √( 1-x？ )

e = 1- x？ -export x on both sides.

2y'e = -2x

y' = -x/e

y''= -[e - x( 1-x？ )]/( 1- x？ ) ?

Substituting the expression of y for sorting is what you want! Please do it and check it again. Thank you!