1×3+2×5+3×7+...+19×39+20×41
1-3+5-7+9-11+13-.-39+41=?
做出这到题1 1/2-2 5/6+3 1/12-4 19/20+5 1/30-6 41/42+7 1/56-8 71/7
(1+1*2)-(2+5*6)+(3+1*12)-(4+19*20)+(5+1*30)-(6+41*42)+(7+1*5
1+2-3-4+5+6-7-8+9+10-.+38-39-40+41=?-
1+1/2-2-5/6+3+1/12-4-19/20+5+1/30-6-41/42+7+1/56-8-71/72+9+1
两道奥数题?31.1 1/2 - 2 5/6 + 3 1/12-4 19/20 + 5 1/30 - 6 41/42 +
1*1+2*3+3*5+4*7+.+20*39怎样简便运算
找规律1:(3,5)(7,13)(9,)( ,19); 2:(20,7)(24,9)(36,)(?,19)
1+3+5+7+9+11+13+15+17+19+21+25+27+29+31+35+37+39+41+43+47+49
那1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 4
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
1-3+5-7+9-11+13-15+17-19+21-23+25-27+29-31+33-35+37-39+41=?