1x2x3+2x3x4+3x4x5+...+7x8x9=,
carole7222022-10-04 11:39:541条回答
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flamebird 共回答了9个问题 |采纳率100%- 因为1x2x3=(1x2x3×4-0x1x2×3)/4
2x3x4=(2x3x4×5-1x2x3×4)/4
.
7x8x9=(7x8x9×10-6x7x8x9)/4
所以 1x2x3+2x3x4+3x4x5+…+7x8x9
=(1x2x3×4-0x1x2×3)/4+(2x3x4×5-1x2x3×4)/4+...(7x8x9×10-6x7x8x9)/4
=(7x8x9×10)/4
=1260 - 1年前
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