(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)

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(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)(9-16/39×4)+(8-16/39×5)+

(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)
(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)

(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)
(9-16/39×4)+(8-16/39×5)+..+(4-16/39×9)
=9+8+7+...+4-16/39×4-16/39×5-.-16/39×9
=(9+4)*6/2-16/39×(9+8+7+...+4)
=(9+4)*6/2-16/39×(9+4)*6/2
=39-16
=23

(9-16/39*4)+(8-16/39*5)+...+(4-16/39*9)
=(9+8+...+4)-16/39*(4+5+...+9)
=23