B1.Tìm A/B biết:
A=4/(7*31)+6/(7*41)+9/(10*41)+7/(10*57)
B=7/(19*31)+5/(19*43)+3/(23*43)+11/(23*57)
B2:CMR:
A=1/52+2/53+3/54+...+11/512 <1/16
Những câu hỏi liên quan
Tính tỉ số A/B biết:
A=4/7×31+6/7×41+9/10×41+7/10×57
B=7/19×31+5/19×43+3/23×43+3/23×43+11/23×57
cho A= 4/31*7 + 6 / 7*41 + 9/10 * 41 + 7/ 10 * 57
B= 7/19*31 + 5/19*43 + 3/23*43 + 11/23*57
tính phân số A/B
Cho A=4/7*31+6/7*41+9/10*41+7/10*57
B=7/19*31+5/19*43+3/23*43+11/23*57
Tinh ti so A/B
Ta có: \(A=\frac{4}{7.31}+\frac{6}{7.41}+\frac{9}{10.41}+\frac{7}{10.57}\)
\(=\frac{20}{35.31}+\frac{30}{35.41}+\frac{45}{50.41}+\frac{35}{50.57}\)
\(=5\left(\frac{4}{31.35}+\frac{6}{35.41}+\frac{9}{41.50}+\frac{7}{50.57}\right)\)
\(=5\left(\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}\right)\)
\(=5\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(B=\frac{7}{19.31}+\frac{5}{19.43}+\frac{3}{23.43}+\frac{11}{23.57}\)
\(=\frac{14}{38.31}+\frac{10}{38.43}+\frac{6}{46.43}+\frac{22}{46.57}\)
\(=2\left(\frac{7}{31.38}+\frac{5}{38.43}+\frac{3}{43.46}+\frac{11}{46.57}\right)\)
\(=2\left(\frac{1}{31}-\frac{1}{38}+\frac{1}{38}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}+\frac{1}{46}-\frac{1}{57}\right)\)
\(=2\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(\Rightarrow\frac{A}{B}=\frac{5\left(\frac{1}{31}-\frac{1}{57}\right)}{2\left(\frac{1}{31}-\frac{1}{57}\right)}=\frac{5}{2}\)
Đúng 2
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M = 4/7×31 + 6/7×41 + 9/10×41 + 7/10×57
N = 7/19×31 + 5/19×43 + 3/23×43 + 11/23×57
Tính M ÷ N
cho A = 4/(7*31)+6/(7*41)+9/(10*41)+11/(10*57)
B = 7/(19*31)+5/(19*43)+3(23*43)+11/(23*57)
tính tỉ A/B
Ta có: A=47.31 +67.41 +910.41 +710.57
=2035.31 +3035.41 +4550.41 +3550.57
=5(431.35 +635.41 +941.50 +750.57 )
=5(131 −135 +135 −141 +141 −150 +150 −157 )
=5(131 −157 )
B=719.31 +519.43 +323.43 +1123.57
=1438.31 +1038.43 +646.43 +2246.57
=2(731.38 +538.43 +343.46 +1146.57 )
=2(131 −138 +138 −143 +143 −146 +146 −157 )
=2(131 −157 )
⇒AB =5(131 −157 )2(131 −157 ) =52
Đúng 0
Bình luận (0)
cho A= 4/7*31 + 6/7*42 + 9/10*41 + 7/10*57 B= 7/19*31 + 5/19*43 + 3/23*43 + 11/23*57
tỉ số A/B là
Cho M=4/31×7+6/4×41+9/10×41+7/10×57
N=7/19×31+5/19×43+3/23×43+11/23×57
Tính M/N
Cho M=4/41*7+6/7*41+9/10*41+7/10*57 N=7/19*31+5/19*43+3/23*43+11/23*57
Tính tỉ số M/N
Làm đúng mình tick cho
H=1/2+1/2^2+1/2^3+...+1/2^2004
I=4/31*7+6/7*41+9/10*41+7/10*57
K=7/19*31+5/19*43+11/23*57
M=4/5*8+4/8*11+3/11*14+...+305*308
Giúp mình nhé!!!