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a: \(=\left(-\dfrac{25}{140}+\dfrac{245}{140}+\dfrac{32}{140}\right)\cdot\dfrac{-69}{20}\)
\(=\dfrac{252}{140}\cdot\dfrac{-69}{20}\)
\(=\dfrac{9}{5}\cdot\dfrac{-69}{20}=\dfrac{-621}{100}\)
b: \(=\left(6-2-\dfrac{4}{5}\right)\cdot\dfrac{25}{8}-\dfrac{8}{5}\cdot4\)
\(=\dfrac{16}{5}\cdot\dfrac{25}{8}-\dfrac{32}{5}=\dfrac{18}{5}\)
c: \(=\left(\dfrac{2}{24}+\dfrac{18}{24}+\dfrac{14}{24}\right):\dfrac{-17}{8}\)
\(=\dfrac{34}{24}\cdot\dfrac{-8}{17}=\dfrac{-1}{3}\cdot2=-\dfrac{2}{3}\)
a) \(2\dfrac{3}{4}.\left(-0,4\right)-1\dfrac{3}{5}.2,75+\left(-1,2\right):\dfrac{4}{11}\)
= \(2,75.\left(-0,4\right)-\left(1,6\right).\left(2,75\right)+\left(-1,2\right).\dfrac{11}{4}\)
= \(2,75.\left(-0,4\right)-\left(1,6\right).\left(2,75\right)+\left(-1,2\right).\left(2,75\right)\)
= \(2,75.\left\{\left(-0,4\right)-\left(1,6\right)+\left(-1,2\right)\right\}\)
= \(2,75.\left(-3,2\right)\)
= \(-8,8\)
b) \(1,4.\dfrac{15}{49}-\left(\dfrac{4}{5}+\dfrac{2}{3}\right):2\dfrac{1}{5}\)
= \(\dfrac{7}{5}.\dfrac{15}{49}-\left(\dfrac{4}{5}+\dfrac{2}{3}\right):\dfrac{11}{5}\)
= \(\dfrac{7}{5}.\dfrac{15}{49}-\dfrac{22}{15}.\dfrac{5}{11}\)
= \(\dfrac{3}{7}-\dfrac{2}{3}\)
= \(-\dfrac{5}{21}\)
c) \(\left(-3,2\right).\dfrac{15}{64}+\left(0,8-2\dfrac{4}{15}\right):3\dfrac{2}{3}\)
= \(-\dfrac{16}{5}.\dfrac{15}{64}+\left(\dfrac{4}{5}-2\dfrac{4}{15}\right):\dfrac{11}{3}\)
= \(-\dfrac{16}{5}.\dfrac{15}{64}+\left(-\dfrac{22}{15}\right).\dfrac{3}{11}\)
= \(\left(-\dfrac{3}{4}\right)+\left(-\dfrac{2}{5}\right)\)
= \(-\dfrac{23}{20}\)
d) \(0,02.\dfrac{-25}{2}+\dfrac{3}{8}+\left(-2\dfrac{9}{20}\right).\dfrac{2}{7}\)
= \(\dfrac{1}{50}.\dfrac{-25}{2}+\dfrac{3}{8}+\left(-\dfrac{49}{20}\right).\dfrac{2}{7}\)
=\(\left(-\dfrac{1}{4}\right)+\dfrac{3}{8}+\left(-\dfrac{7}{10}\right)\)
= \(\dfrac{1}{8}+\left(-\dfrac{7}{10}=\right)\)
= \(-\dfrac{23}{40}\)
e) \(34\%:\dfrac{51}{16}-3\dfrac{7}{9}.6,5-\left(0,4\right)^2\)
= \(\dfrac{17}{50}.\dfrac{16}{51}-\dfrac{34}{9}.\dfrac{13}{2}-\dfrac{4}{25}\)
= \(\dfrac{8}{75}-\dfrac{221}{9}-\dfrac{4}{15}\)
= \(-\dfrac{5501}{225}\)
a: \(=\left(\dfrac{2}{18}-\dfrac{15}{18}-\dfrac{72}{18}\right):\left(\dfrac{21}{36}-\dfrac{1}{36}-\dfrac{360}{36}\right)\)
\(=\dfrac{-85}{18}:\dfrac{-170}{18}\)
\(=\dfrac{85}{170}=\dfrac{1}{2}\)
b: \(=\left(\dfrac{5}{8}-\dfrac{5}{6}-\dfrac{5}{32}+\dfrac{5}{64}\right):\left(1-\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{8}\right)\)
\(=\dfrac{-55}{192}:\dfrac{3}{8}=\dfrac{-55}{192}\cdot\dfrac{8}{3}=-\dfrac{55}{72}\)
bài 1) a) \(1+2+3+4+........+2005+2006\)
\(\Leftrightarrow\) \(\left(1+2006\right)+\left(2+2005\right)+........+\left(1003+1004\right)\)
\(\Leftrightarrow\) \(2007.\dfrac{2006}{2}=2007.1003=2013021\)
b) \(5+10+15+.......+2000+2005\)
\(\Leftrightarrow\) \(\left(2005+5\right)\left(2000+10\right)+.......+\left(1000+1010\right)\)
\(\Leftrightarrow\) \(2010.\dfrac{2005}{5}=2010.401=405010\)
c) \(140+136+132+.......+64+60\)
\(\Leftrightarrow\) \(\left(140+60\right)+\left(136+64\right)+.......+\left(100+100\right)\)
\(\Leftrightarrow\) \(200.10\) = \(2000\)
1)
a) \(1+2+3+4+.....+2005+2006\)
Số các số hạng của dãy trên là:
\((2006-1):1+1=2006\)
Tổng dãy là:
\(\dfrac{2006\left(2006+1\right)}{2}=2013021\)
b) \(5+10+15+.....+2000+2005\)
Số các số hạng của dãy là:
\((2005-5):5+1=401\)
Tổng dãy là:
\(\dfrac{401\left(2005+5\right)}{2}=403005\)
c)\(140+136+132+.....+64+60\)
\(=60+64+.....+132+136+140\)
Số số hạng của dãy là:
\((140-60):4+1=11\)
Tổng dãy là:
\(\dfrac{11\left(60+140\right)}{2}=1100\)
a: \(A=\dfrac{-7}{28}\cdot\dfrac{15}{25}=\dfrac{-1}{4}\cdot\dfrac{3}{5}=\dfrac{-3}{20}\)
b: \(B=\dfrac{-5\cdot7}{14\cdot\left(-3\right)}=\dfrac{35}{42}=\dfrac{5}{6}\)
c: \(C=\dfrac{-1}{5}-\dfrac{1}{5}\cdot\dfrac{3}{5}=\dfrac{-1}{5}-\dfrac{3}{25}=\dfrac{-8}{25}\)
d: \(D=\dfrac{-3}{4}-\dfrac{1}{4}=-1\)
e: \(E=\dfrac{-4}{5}\left(1-\dfrac{15}{16}\right)=\dfrac{-4}{5}\cdot\dfrac{1}{16}=\dfrac{-1}{20}\)
f: \(F=\dfrac{6-7}{4}\cdot\dfrac{4+12}{22}=\dfrac{-1}{4}\cdot\dfrac{8}{11}=\dfrac{-2}{11}\)
A)(-4)*5+15 H)(-4)*4+5*(-10) O) (-5) * (-3) +(-4)^2
= (-20)+15 = -16 + (-15) = 15 + 16
= -5 = -31 = 31
B)(-32)+(-5) * 7 i)99 * (-5)-11*(-7) F) (-1)^3 +(-2) *(-3)
= (-32) + (-35) =-495 - (-77) = -1 + 6
= -67 = -572 = 5
C)(-5) * 2 + (-6) *4 k) (-4)*2+(-2)+12 Q) (-11) * (-4) - (-8 * 5)
= (-10) + (-24) =4 * (-2) + (-2) +12 = 44 + 40
= -34 = (-2) *(4 +12) = 84
D)119-(-14) *10 = (-2) * 16 S) 100 - (-15) * 2
= 119 + 140 = -72 = 100 + 30
=259 L) (-32) +(-15) * (-3) = 130
E)112+(-11)*4 = (-32)+ 45
=112 + (-40) = 13
=72 M) (-12) *3 + (-6) * 5
G)(-22)+ (-2) *6 = -36 + (-30)
= (-22) + (-12) =-66
= -34 N) 100- (-14) * (-3)
=100 + (-42)
= 58
Đáp án B
C = 4 5 : 4 5 . - 5 4 : 16 25 - 1 5 = 4 5 : - 1 : 11 25 = 4 5 . - 1 . 25 11 = - 20 11
D = 15 8 - 15 6 - 15 32 + 15 64 3 - 3 2 - 3 4 + 3 8 = 15 1 8 - 1 6 - 1 32 + 1 64 3 . 1 - 1 2 - 1 4 + 1 8 = 15 . - 11 192 3 . 1 8 = 5 . - 11 72 = - 55 72
Vì - 55 72 > - 20 11 nên D > C