30x29-29x28+28x27-27x26+.....+4x3-3x2
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解决时间 2021-03-10 14:08
- 提问者网友：寂寞梧桐
- 2021-03-10 10:17
30x29-29x28+28x27-27x26+.....+4x3-3x2
最佳答案
- 五星知识达人网友：煞尾
- 2021-03-10 10:33
30x29-29x28+28x27-27x26+.....+4x3-3x2
=（30-28）x29+(28-26)x27+......+(4-2)x3
=2x29+2x27+......+2x3
=2x(29+27+....+3)
=2x[(29+3)x14÷2]
=2x224
=448
=（30-28）x29+(28-26)x27+......+(4-2)x3
=2x29+2x27+......+2x3
=2x(29+27+....+3)
=2x[(29+3)x14÷2]
=2x224
=448
全部回答
- 1楼网友：忘川信使
- 2021-03-10 11:14
=(30x29-29x28)+(28x27-27x26)+.....+(4x3-3x2)
=2x29+2x27+2x25+……+2x3
=2x(29+27+25+……+3)
=2x[(3+29)x14/2]
=448
=2x29+2x27+2x25+……+2x3
=2x(29+27+25+……+3)
=2x[(3+29)x14/2]
=448
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