Question

(9-39分之16*4)+(8-39分之16*5)+···+(4-39分之16*9)简便计算

Answer 1

(9-39分之16*4)+(8-39分之16*5)+···+(4-39分之16*9)

=9+8+7+6+5+4-(16/39*(4+5+6+...+9))

=39-16*39/39

=39-16

=23