Đặt 1/5 + 1/14+1/28 +1/44 + 1/61+1/85+1/97 =A
Ta có : A = 1/5 + ( 1/14+1/28+1/44)+(1/61+1/85+1/97)
A < 1/5 ( 1/14.3)+(1/61.3)
A < 1/5+ 3/14+3/61
A < 1/5 + 3/12+1/20
A < 1/5+1/4+1/20
A < 1/2 ( đpcm)
Đây toán lớp 6,chứ ko phải là toán lớp 7 chứ...
Đặt 1/5 + 1/14+1/28 +1/44 + 1/61+1/85+1/97 =A
Ta có : A = 1/5 + ( 1/14+1/28+1/44)+(1/61+1/85+1/97)
A < 1/5 ( 1/14.3)+(1/61.3)
A < 1/5+ 3/14+3/61
A < 1/5 + 3/12+1/20
A < 1/5+1/4+1/20
A < 1/2 ( đpcm)
Đây toán lớp 6,chứ ko phải là toán lớp 7 chứ...
so sanh
1/5+1/14+1/28+1/44+1/61+1/85+1/97 va 1/2
BT1: So sanh
\(\frac{-13}{39}va-\frac{21}{63}\)
\(\frac{1}{234567}va-\frac{2}{14}\)
BT2: So sanh
\(\frac{-39}{65}va-\frac{21}{35}\)
\(\frac{1}{2012}va-\frac{1}{14}\)
cho A=1+1/2+1/3+1/4+.......+1/4026 va B=1+1/3+1/5+........+1/4025
so sanh A/B va 1/2013/2014
cho A=1/1*2+1/3*4+...+1/99.100
B=7/2
C=5/6
so sanh A&B va so sanh A& C
M=(1/4*9+1/9*14+1/14*19+...1/44*49)*1-3-5-7-9-...-49/89=-9/28
cho a=(1-1/2)*(1-1/3)*(1-1/4)*...(1-1/19)*(1-1/20)
b=(1-1/4)*(1-1/9)*(1-1/16)*...*(1-1/18)*(1-1/180)
so sanh a va 1/21
so sanh b va 11/21
1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 10 * 11 * 12 * 13 * 14 * 15 * 16 * 17 * 18 * 19 * 20 * 21 * 22 * 23 * 24 * 25 * 26 * 27 * 28 * 29 * 30 * 31 * 32 * 33 * 34 * 35 * 36 * 37 * 38 * 39 * 40 * 41 * 42 * 43 * 44 * 45 * 46 * 47 * 48 * 49 * 50 * 51 * 52 * 53 * 54 * 55 * 56 * 57 * 58 * 59 * 60 * 61 * 62 * 63 * 64 * 65 * 66 * 67 * 68 * 69 * 70 * 71 * 72 * 73 * 74 * 75 * 76 * 77 * 78 * 79 * 80 * 81 * 82 * 83 * 84 * 85 * 86 * 87 * 88 * 89 * 90 * 91 * 92 * 93 * 94 * 95 * 96 * 97 * 98 * 99 * 100 bằng bao nhiêu?
so sanh=1/5^300 va+1/3^500
so sanh 1/4+1/16+1/36+1/64+1/100+1/144+1/196 va 1/2