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標題:
數學Arithmetic Sequences既問題 -PLS
發問:
NO1-In each of the following Arithmetic Sequences ,find(i) the number of terms ; (ii) the first negative term.(a) 40, 32 , ...,-32(b)85,79,...,-17N02-Consider all the multiples of 4 from 100 to 999.A(i) How many multiples are there?(ii)Find theSum of these multiples .(b)Hence find the sum of all... 顯示更多 NO1-In each of the following Arithmetic Sequences ,find(i) the number of terms ; (ii) the first negative term. (a) 40, 32 , ...,-32 (b)85,79,...,-17 N02-Consider all the multiples of 4 from 100 to 999. A(i) How many multiples are there? (ii)Find theSum of these multiples . (b)Hence find the sum of all the positive there-digit integers which are NOTT divisible by 4. 更新: a 同b ..唔明,想問下條式係咩>
最佳解答:
(a) The number of term=(40+32)/8+1=10 The first negative term is -8 (b) The number of term=(85+17)/6+1=18 The first negative term is -17+6*2=-5 2 (a)(i) Consider 100+4(n-1)=1000 n=900/4+1=226 So, there are 226-1=225 multiples (ii) S=100+104+...+996 S=225/2[200+(225-1)(4)]=123300 (b) The sum is (1000/2)(100+999)-123300 =426200 2009-06-07 17:15:15 補充： 你用T(n)=a+(n-1)d吧
其他解答:C8D74AB62542840B
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