TINH nhanh
1+(-2)+3+(-4)+57+(-6)+....+19+(-20)
Những câu hỏi liên quan
Tính nhanh
1×2×3×4×5×6×7×8×9×10×11×12×13×14×15×16×17×18×19×20
20 tháng 3 2022 lúc 21:18
Tính nhanh
1+2+3+4+...+19=...
GIÚP EM VỚI
Thuc hien phep tinh hop li(neu co the):
1) 69 .113 - 27. 69 + 69 .14 + 31
2) 90 -(22. 25 - 32. 7)
3) 720 - {40.[(120 - 70) :25 + 23]}
4) 2345 - 1000 :[19 - 2(21 - 18)2]
5) (-23) + 13 + (-17) + 57
6) (-123) + |-13| + (-7)
7) - |-33| +(-15)+ 20 - |45 - 40| - 57
tinh
B=7*6^10*2^20*3^6-2^19*6^15/9*6^19*2^9-4*3^17*2^26
X+4/5x9+4/9x13+4/13x17+...+4/41x55=1X-(20/11x13+20/13x15+20/15x17+...+20/53x55=3/11 so sánh:a,(19/12-11/12)x12/25 và 1/2+3/2-1/3/7/6x3/11 b,2+2/47-2/57/9+9/57-18/87 và 3+3/59-6/87/9+9/59-18/87
Xem chi tiết
a. ( 19 5/8 : 7/12 - 13 1/4 : 7/12) . 4/5
b.( - 2/5 + 3/7) - (4/9 + 12/20 - 13/35) + 7/35
c. ( 4 5/57 - 3/ 4/51 + 8 13/29) - ( 3 5/57 - 6 16/29)
\(\left(19\frac{5}{8}:\frac{7}{12}-13\frac{1}{4}:\frac{7}{12}\right).\frac{4}{5}\)
\(=\left(\frac{157}{8}:\frac{7}{12}-\frac{53}{4}:\frac{7}{12}\right).\frac{4}{5}\)
\(=\left[\left(\frac{157}{8}-\frac{53}{4}\right):\frac{7}{12}\right].\frac{4}{5}\)
\(=\left[\frac{51}{8}:\frac{7}{12}\right].\frac{4}{5}\)
\(=\frac{153}{14}.\frac{4}{5}\)
\(=\frac{306}{35}\)
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\(\left(\frac{-2}{5}+\frac{3}{7}\right)-\left(\frac{4}{9}+\frac{12}{20}-\frac{13}{35}\right)+\frac{7}{35}\)
\(=\frac{1}{35}-\frac{212}{315}+\frac{7}{35}\)
\(=\frac{1}{35}+\frac{-212}{315}+\frac{7}{35}\)
\(=\frac{9}{315}+\frac{-212}{315}+\frac{63}{315}\)
\(=\frac{-140}{315}=\frac{-4}{9}\)
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\(\left(4\frac{5}{57}-3\frac{4}{51}+8\frac{13}{29}\right)-\left(3\frac{5}{57}-6\frac{16}{29}\right)\)
\(=\left(\frac{233}{57}-\frac{157}{51}+\frac{245}{29}\right)-\left(\frac{176}{57}-\frac{190}{29}\right)\)
\(=\frac{1941}{323}-\frac{-5726}{1653}\)
\(=\frac{14011}{1479}\)
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17 tháng 4 2023 lúc 18:47
Tính nhanh
1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)
\(=\dfrac{1}{1}\cdot\dfrac{1}{2}+\dfrac{1}{2}\cdot\dfrac{1}{3}+\dfrac{1}{3}\cdot\dfrac{1}{4}+\dfrac{1}{4}\cdot\dfrac{1}{5}+\dfrac{1}{5}\cdot\dfrac{1}{6}+\dfrac{1}{6}\cdot\dfrac{1}{7}\)
\(=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
\(=\dfrac{1}{1}-\dfrac{1}{7}=\dfrac{7}{7}-\dfrac{1}{7}=\dfrac{6}{7}\)
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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: \(A=\frac{4}{7.31}+\frac{6}{7.41}+\frac{9}{10.41}+\frac{7}{10.57}\)
\(=\frac{20}{35.31}+\frac{30}{35.41}+\frac{45}{50.41}+\frac{35}{50.57}\)
\(=5\left(\frac{4}{31.35}+\frac{6}{35.41}+\frac{9}{41.50}+\frac{7}{50.57}\right)\)
\(=5\left(\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}\right)\)
\(=5\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(B=\frac{7}{19.31}+\frac{5}{19.43}+\frac{3}{23.43}+\frac{11}{23.57}\)
\(=\frac{14}{38.31}+\frac{10}{38.43}+\frac{6}{46.43}+\frac{22}{46.57}\)
\(=2\left(\frac{7}{31.38}+\frac{5}{38.43}+\frac{3}{43.46}+\frac{11}{46.57}\right)\)
\(=2\left(\frac{1}{31}-\frac{1}{38}+\frac{1}{38}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}+\frac{1}{46}-\frac{1}{57}\right)\)
\(=2\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(\Rightarrow\frac{A}{B}=\frac{5\left(\frac{1}{31}-\frac{1}{57}\right)}{2\left(\frac{1}{31}-\frac{1}{57}\right)}=\frac{5}{2}\)
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SGK Kết nối tri thức với cuộc sống - Trang 20
3 tháng 4 2023 lúc 18:47
Tính.
20 + 6 57 – 7 3 + 40
43 + 20 75 – 70 69 – 19
