例1求△(x2),△2(x2),△3(x2): 解 设y=x2,则 △y=△(x2)=(x+1)2-x2=2x+1 △2y.=△2(x2)=△(2x+1) =[2(x+1)+1]-(2x+1)=2 3yx=△3(x2)=2-2=0 经济数学 微积分 例 1 求 ( ), ( ), ( ) 2 2 2 3 2  x  x  x . 解 设y = x 2 ，则( ) ( 1) 2 1 2 2 2 yx =  x = x + − x = x + 2( 1) 1 (2 1) 2 ( ) (2 1) 2 2 2 = + + − + =  =  =  + x x yx x x ( ) 2 2 0 3 3 2  y x =  x = − =