nếu: 1=5
2=8 ,7=9
thì 5=?
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a, \(\dfrac{x}{2}+\dfrac{3x}{4}=\dfrac{4}{5}\Leftrightarrow\dfrac{10x+15x}{20}=\dfrac{16}{20}\Rightarrow25x=16\Leftrightarrow x=\dfrac{16}{25}\)
b, \(\dfrac{3}{7}.\dfrac{5}{8}-\dfrac{3}{8}.\dfrac{13}{8}+\dfrac{1}{7}=\dfrac{15}{56}-\dfrac{39}{64}+\dfrac{1}{7}\)
\(=\dfrac{120}{448}-\dfrac{273}{448}+\dfrac{64}{448}=-\dfrac{89}{448}\)
Lời giải chi tiết:
8 + 1 = 9 | 7 – 5 = 2 | 5 + 2 = 37 | 10 – 6 = 4 |
28 + 1 = 29 | 57 – 5 = 52 | 7 – 35 = 2 | 52 + 0 = 52 |
45 + 2 = 47 | 49 – 6 = 43 | 7 – 2 = 35 | 99 – 8 = 91 |
8+1=9
7-5=2
5+2=7
10-6=4
28+1=29
57-5=52
7-35=-28
52+0=52
OKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK
1 + 6 + 5 + 4 + 7 + 8 + 9 + 5 + 5 + 6 +52 + 2 + 5 + 5 = 120
a) 5 + (-8) . 3 = 5 + (-24) = -19
b) 4 + - 5 2 = 4 + 25 = 29
c) 1 – 2 – 3 + 4 + 5 – 6 – 7 + 8 + … + 801 – 802 – 803 + 804
= (1 – 2 – 3 + 4) + (5 – 6 – 7 + 8) + … + (801 – 802 – 803 + 804)
= 0 + 0 + … + 0 = 0
F = 7 + 72 + 73 + 74 + ..... + 7100
F= 7+(1+7)+73+(1+7)+...+799+(1+7)
F = 7x8+73x8+...+799x8
F= 8x(7+73+...+799)
mà 8 chia hết 8 => 8(7+73+...+799) chia hết 8
Vậy F chia hết cho 8
\(B=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+\frac{1}{18\cdot19\cdot20}\)
\(B=\frac{1}{2}\left(\frac{2}{1\cdot2\cdot3}+\frac{2}{2\cdot3\cdot4}+\frac{2}{3\cdot4\cdot5}+\frac{2}{18\cdot19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{2\cdot3}+\frac{1}{2\cdot3}-\frac{1}{3\cdot4}+\frac{1}{3\cdot4}-\frac{1}{4\cdot5}+...+\frac{1}{18\cdot19}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\cdot\frac{189}{380}=\frac{189}{760}\)
\(C=\frac{52}{1\cdot6}+\frac{52}{6\cdot11}+\frac{52}{11\cdot16}+...+\frac{52}{31\cdot36}\)
\(C=\frac{52}{5}\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+\frac{5}{11\cdot16}+...+\frac{6}{31\cdot36}\right)\)
\(C=\frac{52}{5}\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{31}-\frac{1}{36}\right)\)
\(C=\frac{52}{5}\cdot\left(1-\frac{1}{36}\right)\)
\(C=\frac{91}{9}\)
5 = 1 thid phải
thì 5=1