例4.求函数y=√x的导数 解:(1)亼y=√x+Ax-√x (2) x+△v △x(√x+△x+√x)√x+△x+ (3)y=lim=lm - >0√x+△x+
结束 解 例 4 求函数 y = x 的导数 解 ( 1 ) y = x + x − x (2) x x x x x x x x x x x x xy + + = + + = + − = 1 ( ) (3) x x x x x y y x x 2 1 1 lim lim 0 0 = + + = = → → (2) x x x x x x x x x x x x xy + + = + + = + − = 1 ( ) (2) x x x x x x x x x x x x xy + + = + + = + − = 1 ( ) (3) x x x x x y y x x 2 1 1 lim lim 0 0 = + + = = → → (3) x x x x x y y x x 2 1 1 lim lim 0 0 = + + = = → →