若13+15+17+.....+99=m的二次方-n的二次方,求數對(m,n)?
回答 (2)
Sol
(99-13)/2+1=44
13+15+17+…+99=(13+99)*44/2=2464
2464=(2^5)*7*11
2464有(5+1)*(1+1)*(1+1)=24個正因數
分別為1,2,4,7,8,11,14,16,22,28,32,44,56,77,88,112,154,176,224,308,352,616,1232,2464
2464=1*2464
2464=2*1232
2464=4*616
2464=7*352
2464=8*308
2464=11*224
2464=14*176
2464=16*154
2464=22*112
2464=28*88
2464=32*77
2464=44*56
m^2-n^2=2464
(m-n)(m+n)=2464
(1) m-n=1,m+n=2464
2m=2465(不合)
(2) m-n=2,m+n=1232
2m=1234
m=617,n=615……………….
(3) m-n=4,m+n=616
2m=620
m=310,n=306……………….
(4) m-n=7,m+n=352
2m=359 (不合)
(5) m-n=8,m+n=308
2m=316
m=158,n=150……………….
(6) m-n=11,m+n=2246
2m=235(不合)
(7) m-n=14,m+n=176
2m=190
m=95,n=81………………….
(8) m-n=16,m+n=154
2m=170
m=85,n=69………………….
(9) m-n=22,m+n=112
2m=134
m=67,n=45………………….
(10) m-n=28,m+n=88
2m=116
m=58,n=30………………….
(11) m-n=32,m+n=77
2m=109(不合)
(12) m-n=44,m+n=56
2m=100
m=50,n=6..………………….
m = ±50, n = ±6
m = ±58, n = ±30
m = ±67, n = ±45
m = ±85, n = ±69
m = ±95, n = ±81
m = ±158, n = ±150
m = ±310, n = ±306
m = ±617, n = ±615
收錄日期: 2021-04-16 17:11:07
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