等差数列3,10,17,„,2005与3,8,13,„,2003中,值相同的项有?个
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![等差数列3,10,17,„,2005与3,8,13,„,2003中,值相同的项有?个](/uploads/image/z/1087169-41-9.jpg?t=%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%973%2C10%2C17%2C%26%238222%3B%2C2005%E4%B8%8E3%2C8%2C13%2C%26%238222%3B%2C2003%E4%B8%AD%2C%E5%80%BC%E7%9B%B8%E5%90%8C%E7%9A%84%E9%A1%B9%E6%9C%89%3F%E4%B8%AA)
等差数列3,10,17,„,2005与3,8,13,„,2003中,值相同的项有?个
等差数列3,10,17,„,2005与3,8,13,„,2003中,值相同的项有?个
等差数列3,10,17,„,2005与3,8,13,„,2003中,值相同的项有?个
an=3+(n-1)*7=7n-4 —— n=1,2,...,287
bm=3+(m-1)*5=5m-2 ——m=1,2,...,401
an= 7n-4=5m-2 =bn
7n-5m=2
实数5m个位数必然为5或0,则7n个位数必然为7或2,n与7的乘数若要个位数为7或2,则n的个位数为1或6
(1,1)(6,8) ——2
(11,15)(16,22) (21,29)(26,)...(91,)(96,) ——2*9=18
(101,141)(106,148)(111,155)(116,162)...(191,)(196,) ——2*10=20
(201,)(206,)...(281,)(286,400) ——2*9=18
2+18+20+18=58