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SP
1
18 tháng 7 2016
a) 136 x 68 + 16 x 272 = 136 x 68 + 16 x 2 x 136 = 136 x 68 + 32 x 136 = 136 x ( 68 + 32 ) = 136 x 100 = 13600
b) 8 x 9 x14 + 6 x 17 x 12 + 19 x 4 x18 = 2 x 4 x9 x 14 + 6 x 17 x 4 x 3 + 19 x 4 x 18
= 56 x 18 + 18 x 68 + 76 x 18 = 18 x ( 56 + 68 + 76 ) = 18 x 200 = 3600
H9
HT.Phong (9A5)
CTVHS
9 tháng 8 2023
a) \(\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{10}{16}+\dfrac{10}{24}\)
\(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)
\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)
\(=1+1\)
\(=2\)
b) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{14}{6}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=3+2+2\)
\(=7\)
c) \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
\(=1-\dfrac{1}{7}\)
\(=\dfrac{6}{7}\)
20 tháng 9 2023
a. ( 23 - 21) + ( 19 - 17) + ( 15 - 13) + ( 11 - 9) + ( 7 - 5) + ( 3 - 1)
= 2 + 2 + 2 + 2 + 2 + 2
= 2 x 6
= 12
b. ( 24 - 22 ) + ( 20 - 18 ) + ( 16 - 14 ) + ( 12 - 10) + ( 8 - 6 ) + ( 4 - 2)
= 2 + 2 + 2 + 2 + 2 + 2
= 2 x 6
= 12
9 tháng 2 2017
a) \(24\left(16-5\right)-16\left(24-5\right)\)
\(=24.16-24.5-16.24+16.5\)
\(=\left(24.16-16.24\right)-24.5+16.5\)
\(=5\left(-24+16\right)\)
\(=5\left(-8\right)\)
\(=-40\)
b) \(29\left(9-13\right)-19\left(29-13\right)\)
\(=29.9-29.13-19.29+19.13\)
\(=\left(29.9-19.29\right)-\left(29.13-19.13\right)\)
\(=29\left(9-19\right)-13\left(29-19\right)\)
= \(29.\left(-10\right)-13.10\)
\(=-290-130\)
\(=-420\)
c) \(31.\left(-18\right)+31.\left(-81\right)-31\)
\(=31\left[-18+\left(-81\right)\right]-31\)
\(=31.\left(-99\right)-31\)
\(=31\left(-99-1\right)\)
\(=31.\left(-100\right)\)
\(=-3100\)
d) \(-12.47+\left(-12\right).52+\left(-12\right)\)
\(=-12\left(47+52+1\right)\)
\(=-12.100\)
\(=-1200\)
e) \(\left(-6-2\right)\left(-6+2\right)\)
= \(-8.\left(-4\right)\)
\(=32\)
\(f\)) \(\left(-5+9\right)\left(-4\right)\)
\(=4.\left(-4\right)\)
\(=-16\)
LN
8 tháng 7 2018
\(\frac{19}{13}+\frac{14}{16}+\frac{1}{9}+\frac{4}{6}+\frac{7}{13}+\frac{17}{9}\)
\(=\left(\frac{19}{13}+\frac{7}{13}\right)+\left(\frac{14}{6}+\frac{4}{6}\right)+\left(\frac{1}{9}+\frac{17}{9}\right)\)
\(=2+3+2\)
\(=7\)
chúc bạn học tootrs nha
BT
2
28 tháng 6 2018
a, \(\dfrac{38}{7}\) + ( \(\dfrac{16}{7}\) - \(\dfrac{5}{3}\))
= \(\dfrac{38}{7}\) + \(\dfrac{16}{7}\) - \(\dfrac{5}{3}\)
= \(\dfrac{54}{7}\) - \(\dfrac{5}{3}\)
= \(\dfrac{162}{21}\) - \(\dfrac{35}{21}\)
= \(\dfrac{127}{21}\)
b, \(\dfrac{29}{9}\) - ( \(\dfrac{14}{9}\) + \(\dfrac{11}{9}\) )
= \(\dfrac{29-14-11}{9}\)
= \(\dfrac{4}{9}\)
c, ( \(\dfrac{2}{7}\) + \(\dfrac{3}{8}\) + \(\dfrac{12}{7}\) + \(\dfrac{5}{8}\) ) - \(\dfrac{19}{63}\)
= ( \(\dfrac{2+12}{7}\) + \(\dfrac{3+5}{8}\)) - \(\dfrac{19}{63}\)
= \(\left(1+2\right)\) - \(\dfrac{19}{63}\)
= \(3-\dfrac{19}{63}\)
= \(\dfrac{189}{63}\) - \(\dfrac{19}{63}\)
= \(\dfrac{170}{63}\)
d, \(\dfrac{3}{7}\) . \(\dfrac{4}{9}\) + \(\dfrac{4}{9}\) . \(\dfrac{4}{7}\) - \(\dfrac{4}{9}\)
= \(\dfrac{4}{9}\) . ( \(\dfrac{3}{7}\) + \(\dfrac{3}{7}\) ) - \(\dfrac{4}{9}\)
= \(\dfrac{4}{9}\) . \(1-\dfrac{4}{9}\)
= \(\dfrac{4}{9}\) - \(\dfrac{4}{9}\)
= 0
KV
4 tháng 12 2023
a) 1/2 + 3/4 - (3/4 - 4 - 5)
= 1/2 + 3/4 - 3/4 + 4 + 5
= (3/4 - 3/4) + (4 + 5) + 1/2
= 0 + 9 + 1/2
= 19/2
b) [9/16 + 8/(-27)] - (19/27- 7/16 - 2)
= 9/16 - 8/27 - 19/27 + 7/16 + 2
= (9/16 + 7/16) + (-8/27 - 19/27) + 2
= 1 - 1 + 2
= 2
c) -5/8 . [4/9 + 7/(-12)]
= -5/8 . (-5/36)
= 25/288
d) 7/10 . (-3/5) + 7/10 . (-2/5) - (-3/10)
= 7/10 . (-3/5 - 2/5) + 3/10
= 7/10 . (-1) + 3/10
= -2/5
e) -3/7 . 5/9 + 4/9 . (-3/7) + 2 3/7
= -3/7 . (5/9 + 4/9) + 17/7
= -3/7 . 1 + 17/7
= 2
f) 8 2/7 - (3 4/9 + 4 2/7)
= 8 + 2/7 - 3 - 4/9 - 4 - 2/7
= (8 - 3 - 4) + (2/7 - 2/7) - 4/9
= 1 - 4/9
= 5/9
h) 3.(-1/2)² - (4/5 + 8/15) : 5/6
= 3.1/4 - 4/3 : 5/6
= 3/4 - 8/5
= -17/20
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
16 tháng 12 2023
Em nến gõ bằng công thức toán học em nhé. Như vậy mọi người nới hiểu đúng đề bài để trợ giúp cho em một cách tốt nhất em ạ!
-[(-9)-16]-[-(-9)-(-12)-(-19)]
= -[-9-16]-[9+12+19]
= 9+16-9-12-19
= (9-9)+(16-12-19)
= 0-15
= -15
<Áp dụng quy tắc bỏ dấu ngoặc>
-[(-9)-16]-[-(-9)-(-12)-(-19)]
=-[-9-16]-[9+12+19]
=9+16-9-12-19
=(9-9-19)+(16-12)
=-19+4
=-15