+#-*-coding:utf-8-*- 
+import math
+a=3
#dx=0.1
+f1=(math.pow(3+0.1,a)-math.pow(3,a))/0.1
+print 'f1=',f1
+#dx=0.01
+f2=(math.pow93+0.01,a)-math.pow(3,a))/0.001
+print 'f1=',f1,'f2=',f2 
+#dx=0.001 
+f3=(math.pow(3+0.001,a)-math.pow(3,a))/0.001 
+print 'f1=',f1,'f2=',f2,'f3=',f3 
+#dx=0.0001 
+f4=(math.pow(3+0.0001,a)-math.pow(3,a))/0.0001
+print 'f1=',f1,'f2=',f2,'f3=',f3,'f4=',f4
+import math
+a=3
+#dx=0.01
+f1=(math.pow(3*a+0.1*a,a-1)-math.pow(3*a,a-1))/0.1 
+print 'f1',f1
+#dx=0.01
+f2=(math.pow(3*a+0.01*a,a-1)-math.pow(3*a,a-1))/0.01 
+print 'f1=',f1,'f2=',f2
+#dx=0.0001
+f3=(math.pow(3*a+0.001*a,a-1)-math.pow(3*a,a-1))/0.001 
+print 'f1=',f1,'f2=',f2,'f3=',f3
+#dx=0.0001
+f4=(math.pow(3*a+0.0001*a,a-1)-math.pow(3*a,a-1))/0.0001 
+print 'f1=',f1,'f2=',f2,'f3=',f3,'f4='f4