计算:11+2+11+2+3+11+2+3+4+…+11+2+3+4+L+10.-数学

题目简介

计算:11+2+11+2+3+11+2+3+4+…+11+2+3+4+L+10.-数学

题目详情

计算:
1
1+2
+
1
1+2+3
+
1
1+2+3+4
+…+
1
1+2+3+4+L+10
题型:解答题难度:中档来源:不详

答案

class="stub"1
1+2
+class="stub"1
1+2+3
+class="stub"1
1+2+3+4
+…+class="stub"1
1+2+3+4+…+10

=class="stub"2
2×(1+2)
+class="stub"2
3×(1+3)
+class="stub"2
4×(1+4)
+…+class="stub"2
10×(1+10)

=class="stub"2
2
-class="stub"2
3
+class="stub"2
3
-class="stub"2
4
+class="stub"2
4
-class="stub"2
5
+…+class="stub"2
10
-class="stub"2
11

=1-class="stub"2
11

=class="stub"9
11

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