简便方法计算:13×5+15×7+17×9+…+197×9923+29+227+281+2243.-数学

题目简介

简便方法计算:13×5+15×7+17×9+…+197×9923+29+227+281+2243.-数学

题目详情

简便方法计算:
1
3×5
+
1
5×7
+
1
7×9
+…+
1
97×99
2
3
+
2
9
+
2
27
+
2
81
+
2
243
题型:解答题难度:中档来源:不详

答案

(1)class="stub"1
3×5
+class="stub"1
5×7
+class="stub"1
7×9
+…+class="stub"1
97×99

=2×(class="stub"1
3
-class="stub"1
5
+class="stub"1
5
-class="stub"1
7
+class="stub"1
7
-class="stub"1
9
+…+class="stub"1
97
-class="stub"1
99
),
=2×(class="stub"1
3
-class="stub"1
99
),
=2×class="stub"32
99

=class="stub"64
99


(2)class="stub"2
3
+class="stub"2
9
+class="stub"2
27
+class="stub"2
81
+class="stub"2
243

=class="stub"242
243

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