. (20 . 2^4 -12 . 2^3 -48 . 2^2) ^2 : (-8)^3
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1) 1/3 x 1/2 x 3/7 = 3/42 = 1/14
2) 5/4 x 1/3 +1/7 = 5/12 + 1/7 = 35/84 + 12/84 = 47/84
3) 8 x ( 8/9 - 2/3 ) = 8 x 2/9 = 16/9
4) 5/6 x 48/20 x 1/2 = 240/240 = 1
5) ( 2/5 + 3/4 ) + 8 = 23/20 + 8 = 23//20 + 160/20 = 183/20
6) 10 x ( 1/2 - 1/5 ) = 10 x 3/10 = 10/1 x 3/10 = 30/10 = 3
1: \(=\dfrac{1}{3}\cdot\dfrac{3}{7}\cdot\dfrac{1}{2}=\dfrac{1}{7\cdot2}=\dfrac{1}{14}\)
2: =5/12+1/7
=35/84+12/84=47/84
3: =8(8/9-6/9)
=8*2/9=16/9
4: \(=\dfrac{5}{12}\cdot\dfrac{12}{5}=1\)
5: =16/5+6
=16/5+30/5=46/5
6: =10*1/2-10*1/5
=5-2=3
= [-2 + 4] + [-6+8] + ... +[-18 + 20]
= 2 + 2 + ... + 2
= 10
(-2) + 4 + ( -6) + 8 + (-10) + 12 + (-14) + 16 + (-18) + 20
=[(-2) + 12] + [4+(-14)] + [(-6)+16] + [8+(-18)] + [(-10)+20]
= 10 + (-10) + 10 + (-10) + 10
=(10 +10 +10) + [(-10) + (-10)]
= 30 + (-20)
= 10
a) 4+2/5=22/5
b) 5/4+2=13/4
c) 3+3/2=9/2
d) 3/4-1/8=5/8
e) 17/15-7/10=13/30
g) 25/12-15/8=5/24
h) 5-4/3=11/3
i)15/4-3=3/4
a)\(\dfrac{4}{1}+\dfrac{2}{5}=\dfrac{20}{5}+\dfrac{2}{5}=\dfrac{22}{5}\)
b)\(\dfrac{5}{4}+\dfrac{2}{1}=\dfrac{5}{4}+\dfrac{8}{4}=\dfrac{13}{4}\)
c)\(\dfrac{3}{1}+\dfrac{3}{2}=\dfrac{6}{2}+\dfrac{3}{2}=\dfrac{9}{2}\)
d)\(\dfrac{3}{4}-\dfrac{1}{8}=\dfrac{6}{8}-\dfrac{1}{8}=\dfrac{5}{8}\)
e)\(\dfrac{17}{15}-\dfrac{7}{10}=\dfrac{34}{30}-\dfrac{21}{30}=\dfrac{13}{30}\)
g)\(\dfrac{25}{12}-\dfrac{15}{8}=\dfrac{50}{24}-\dfrac{45}{24}=\dfrac{5}{24}\)
h)\(\dfrac{5}{1}-\dfrac{4}{3}=\dfrac{15}{3}-\dfrac{4}{3}=\dfrac{11}{3}\)
i)\(\dfrac{15}{4}-\dfrac{3}{1}=\dfrac{15}{4}-\dfrac{12}{4}=\dfrac{3}{4}\)
\(\left(x+2\right)-2=0\)
\(\Rightarrow x+2-2=0\)
\(\Rightarrow x=0\)
\(\left(x+3\right)+1=7\)
\(\Rightarrow x+3+1=7\)
\(\Rightarrow x+4=7\)
\(\Rightarrow x=3\)
\(\left(3x-4\right)+4=12\)
\(\Rightarrow3x-4+4=12\)
\(\Rightarrow3x=12\)
\(\Rightarrow x=4\)
\(\left(5x+4\right)-1=13\)
\(\Rightarrow5x+4-1=13\)
\(\Rightarrow5x+3=13\)
\(\Rightarrow5x=10\)
\(\Rightarrow x=2\)
\(\left(4x-8\right)-3=5\)
\(\Rightarrow4x-8-3=5\)
\(\Rightarrow4x-11=5\)
\(\Rightarrow4x=16\)
\(\Rightarrow x=4\)
\(8-\left(2x+4\right)=2\)
\(\Rightarrow8-2x-4=2\)
\(\Rightarrow4-2x=2\)
\(\Rightarrow2x=2\)
\(\Rightarrow x=1\)
\(7+\left(5x+2\right)=14\)
\(\Rightarrow7+5x+2=14\)
\(\Rightarrow9+5x=14\)
\(\Rightarrow5x=5\)
\(\Rightarrow x=1\)
\(5-\left(3x-11\right)=1\)
\(\Rightarrow5-3x+11=1\)
\(\Rightarrow16-3x=1\)
\(\Rightarrow3x=15\)
\(\Rightarrow x=5\)
\(\dfrac{-2}{9}\cdot\dfrac{7}{15}+\dfrac{-2}{9}\cdot\dfrac{8}{15}+\dfrac{2}{3^2}\)
\(=-\dfrac{2}{9}\left(\dfrac{7}{15}+\dfrac{8}{15}\right)+\dfrac{2}{9}\)
\(=\dfrac{-2}{9}+\dfrac{2}{9}\)
=0
=>Chọn C
\(=\dfrac{\left(20\cdot16-12\cdot8-48\cdot4\right)^2}{-2^9}=\dfrac{2^{10}}{-2^9}=-2\)