求1-3+2-6+3-9+…+33-99的值已知:1+2+3+4+5+…+31+32+33=17×33

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求1-3+2-6+3-9+…+33-99的值已知:1+2+3+4+5+…+31+32+33=17×33

求1-3+2-6+3-9+…+33-99的值已知:1+2+3+4+5+…+31+32+33=17×33
求1-3+2-6+3-9+…+33-99的值
已知:1+2+3+4+5+…+31+32+33=17×33

求1-3+2-6+3-9+…+33-99的值已知:1+2+3+4+5+…+31+32+33=17×33
1-3+2-6+3-9+…+33-99
= 1+2+3+...+33 -3-6-9-...-99
= (1+2+3+...+33)- 3(1+2+3+...+33)
= -2(1+2+3+...+33)
= -2*17*33
= -1122

17*33-(3+99)*33/2=-1122

=1+2+3+4+5+...+31+32+33-3-6-9-...-99
=1+2+3+...+33-3(1+2+3+...33)
=17*33-3*17*33
=2*17*33
=1122

.....
1-3+2-6+3-9+.......+33-99
=1+2+3+...+33-3-6-9-.......-99
=17*33-3(1+2+3+....+33)
=17*33-3*17*33
=-2*17*33