已知由1至n所有自然數的和的公式是S=1/2n(n+1)
a) 若S1=1+2+3+...+70.求S1的值.
b)若S4=2+4+6+...+140,試以S1表示S4,並求S4的值.
數學題Form.2
2008-03-03 1:25 am
回答 (2)
2008-03-03 5:02 am
✔ 最佳答案
a) S1=(70*(70+1))/2=2485
b) S4=2*(1+2+3+.......+70)
=2*S1
=2*2485
=4970
2008-03-03 6:57 am
a) S1= 1/2(70x(70+1)
=1/2(70x71)
=2485
B) S4=2(S1)
=2x2485
=4970
=1/2(70x71)
=2485
B) S4=2(S1)
=2x2485
=4970
收錄日期: 2021-05-02 18:33:52
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