NT
Nguyen Tran Thanh Cong
11 tháng 8 2017
Tính A:B
Đúng(0)
K
Khách
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PT
11 tháng 8 2017
\(A=\dfrac{4}{7.31}+\dfrac{6}{7.41}+\dfrac{9}{10.41}+\dfrac{7}{10.57}\)
\(A=\dfrac{20}{35.31}+\dfrac{30}{35.31}+\dfrac{45}{50.41}+\dfrac{35}{50.57}\)
\(A=5.\left(\dfrac{4}{35.31}+\dfrac{6}{35.41}+\dfrac{9}{50.41}+\dfrac{7}{50.57}\right)\)
\(A=5.\left(\dfrac{1}{31}-\dfrac{1}{35}+\dfrac{1}{35}-\dfrac{1}{41}+\dfrac{1}{41}-\dfrac{1}{50}+\dfrac{1}{50}-\dfrac{1}{57}\right)\)
\(A=5.\left(\dfrac{1}{31}-\dfrac{1}{57}\right)\)
\(B=\dfrac{7}{19.31}+\dfrac{5}{19.43}+\dfrac{3}{23.43}+\dfrac{11}{23.57}\)
\(B=\dfrac{14}{34.31}+\dfrac{10}{38.43}+\dfrac{6}{46.43}+\dfrac{22}{46.57}\)
\(B=2.\left(\dfrac{7}{34.31}+\dfrac{5}{38.43}+\dfrac{3}{46.43}+\dfrac{11}{46.57}\right)\)
\(B=2.\left(\dfrac{1}{31}-\dfrac{1}{34}+\dfrac{1}{34}-\dfrac{1}{43}+\dfrac{1}{43}-\dfrac{1}{46}+\dfrac{1}{46}-\dfrac{1}{57}\right)\)
\(B=2.\left(\dfrac{1}{31}-\dfrac{1}{57}\right)\)
\(\Rightarrow\dfrac{A}{B}=\dfrac{5.\left(\dfrac{1}{31}-\dfrac{1}{57}\right)}{2.\left(\dfrac{1}{31}-\dfrac{1}{57}\right)}\)
\(\Rightarrow\dfrac{A}{B}=\dfrac{5}{2}\)
26 tháng 3 2018
C = 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/37 - 1/39
= 1/3 - 1/39
= 4/13
Xin lỗi , mình chỉ biết câu C thôi
27 tháng 3 2018
B = 4/7.31 + 6/7.41 + 9/10.41 + 7/10.57
B/5 = 4/35.31 + 6/ 35.41 + 9/50.41 + 7/50.57
= 1/31 - 1/35 + 1/35 - 1/41 + 1/41 - 1/50 + 1/50 - 1/57
= 1/31 - 1/57
B = (1/31-1/57) .5 = 130/1767
mình ko biết đúng hay sai nữa
19 tháng 8 2017
Bai de vcl
A=4/7.31+6/7.41+9/10.41+7/10.57
A=20/35.31+30/35.31+45/50.41+35/50.57
A=5.(4/35.31+6/35.41+9/50.41+7/50.57)
=5.(1/31-1/35+1/35-1/41+1/41-1/50+1/50-1/57)
A=5.(1/31-1/57)
B=7/19.31+5/19.43+3/23.43+11/23.57
B=14/34.31+10/38.43+6/46.43+22/46.57
B=2.(7/34.31+5/38.43+3/46.43+11/46.57
B=2.(1/31-1/34+1/34-1/43+1/43-1/46+1/46-1/57)
B=2.(1/31-1/57)
5.(1/31-1/57)
Vay A/B=5/2
dau /la phan so do
TS
5
11 tháng 3 2023
A=
7.31
4
+
7.41
6
+
10.41
9
+
10.57
7
⇒
5
A
=
35.31
4
+
35.41
6
+
50.41
9
+
50.57
7
\dfrac{A}{5}=\dfrac{1}{31}-\dfrac{1}{35}+\dfrac{1}{35}-\dfrac{1}{41}+\dfrac{1}{41}-\dfrac{1}{50}+\dfrac{1}{50}-\dfrac{1}{57}
5
A
=
31
1
−
35
1
+
35
1
−
41
1
+
41
1
−
50
1
+
50
1
−
57
1
\dfrac{A}{5}=\dfrac{1}{31}-\dfrac{1}{57}=\dfrac{26}{31.57}\Rightarrow A=\dfrac{130}{31.57}
5
A
=
31
1
−
57
1
=
31.57
26
⇒A=
31.57
130
PH
1
24 tháng 5 2016
\(\frac{A}{5}=\frac{4}{35.31}+\frac{6}{35.41}+\frac{9}{50.41}+\frac{7}{50.57}=\frac{35-31}{35.31}+\frac{41-35}{35.41}+\frac{50-41}{50.41}+\frac{57-50}{50.57}\)
\(\frac{A}{5}=\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}=\frac{1}{31}-\frac{1}{57}\)=> A = 5. \(\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(\frac{B}{2}=\frac{7}{38.31}+\frac{5}{38.43}+\frac{3}{43.46}+\frac{11}{46.57}=\frac{38-31}{31.38}+\frac{43-38}{38.43}+\frac{46-43}{43.46}+\frac{57-46}{46.57}\)
\(\frac{B}{2}=\frac{1}{31}-\frac{1}{38}+\frac{1}{38}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}+\frac{1}{46}-\frac{1}{57}=\frac{1}{31}-\frac{1}{57}\)=> B = 2.\(\left(\frac{1}{31}-\frac{1}{57}\right)\)
A/B = 5/2
PM
1
LT
11 tháng 8 2017
A = \(\frac{4}{7}.31+\frac{6}{7}.41+\frac{9}{10}.41+\frac{7}{10}.57\)
= \(\left[\left(\frac{4}{7}+\frac{6}{7}\right).\left(31+41\right)\right]+\left[\left(\frac{9}{10}+\frac{7}{10}\right).\left(41+57\right)\right]\)
= \(\frac{10}{7}.72+\frac{8}{5}.98\)
= \(\left(\frac{10}{7}+\frac{8}{5}\right).\left(72+98\right)\)
= \(\left(\frac{50}{35}+\frac{56}{35}\right).170\)
= \(\frac{106}{35}.170\)
= \(\frac{3604}{7}\)
B = \(\frac{7}{19}.31+\frac{5}{19}.43+\frac{3}{23}.43+\frac{11}{23}.57\)
= \(\left[\left(\frac{7}{19}+\frac{5}{19}\right).\left(31+43\right)\right]+\left[\left(\frac{3}{23}+\frac{11}{23}\right).\left(43+57\right)\right]\)
= \(\frac{12}{19}.74+\frac{14}{23}.100\)
= \(\left(\frac{12}{19}+\frac{14}{23}\right).\left(100+74\right)\)
= \(\left(\frac{276}{437}+\frac{266}{437}\right).174\)
= \(\frac{542}{437}.174\)
= \(\frac{79674}{437}\)
A : B = \(\frac{3604}{7}:\frac{19674}{437}=\frac{3604.437}{7.19674}=\frac{1802.2.437}{7.9837.2.}=\frac{1802.437}{7.9837}\)
KS
1
9 tháng 4 2019
A=4/(7.31)+6/(7.41)+9/(10.41)+7/(10.51)
=20/(35.31)+30/(35.41)+45/(50.41)
+35/(50.51)
=5[4/(35.31)+6/(35.41)+9/(50.41)
+7/(50.51)]
=5(1/31-1/35+1/35-1/41+1/41-1/50
+1/50-1/57)
=5(1/31-1/57)
B=7/(19.31)+5/(19.43)+3/(23.43)
+11/(23.57)
tương tự ta nhân cả tử và mẫu của các phân số biểu thức B với 2
=>B=2(1/31-1/57)
=>A/B=5/2
