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a)=(4.25).37
=100.37
=3700
b)=(132+868)+(763+237)+29
=1000+1000+29
=2029
c)=72+[131-1.20]
=49+[131-20]
=49+111
=160
\(112\cdot35+112\cdot65+800\)
\(=112\cdot\left(35+65\right)+800\)
\(=112\cdot100+800\)
\(=11200+800\)
\(=12000\)
Bài 2:
Ta thấy: 52 > 4.5
62 > 5.6
72 > 6.7
....
20172 > 2016.2017
\(\Rightarrow\)\(\frac{1}{5^2}< \frac{1}{4.5}\)
\(\frac{1}{6^2}< \frac{1}{5.6}\)
\(\frac{1}{7^2}< \frac{1}{6.7}\)
....
\(\frac{1}{2017^2}< \frac{1}{2016.2017}\)
Cộng vế với nhau, ta có:
\(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2017^2}\) < \(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{2016.2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{2016}-\frac{1}{2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}-\frac{1}{2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}\)( vì \(\frac{1}{2017}>0\))
k giúp mik ✅
(-12) + (-18)
= -30
------------------
(-90) + 27 + (-10) + 73
= [(-90) + (-10) + (27 + 73)
= -100 + 100
= 0
---------------------------------
25 . (-5) . (-4)
= 25 . (-4) . (-5)
= -100 . (-5)
= 100 . 5
= 500
----------------------------------------
(-15) . 40 : 6
= [(-15) . 40] : 6
= (-600) : 6
= -100
-----------------------------------
(-27) . 58 + (-27) . 42
= (-27) . (58 + 42)
= (-27) . 100
= -2700
a) \(583+27+417+73\)
\(=\left(583+417\right)+\left(73+27\right)\)
\(=1000+100\)
\(=1100\)
b) \(125\cdot25\cdot4\cdot8\cdot7\)
\(=\left(125\cdot8\right)\cdot\left(25\cdot4\right)\cdot7\)
\(=1000\cdot100\cdot7\)
\(=700000\)
c) \(87-\left[61+\left(7-4\right)^2\right]\)
\(=87-\left(61+3^2\right)\)
\(=87-\left(61+9\right)\)
\(=87-70\)
\(=17\)
d) \(135\cdot47+135\cdot52+135\cdot2021^0\)
\(=135\cdot\left(47+52+2021^0\right)\)
\(=135\cdot\left(99+1\right)\)
\(=135\cdot100\)
\(=13500\)
1)
a)
\(\frac{-5}{6}.\frac{120}{25}< x< \frac{-7}{15}.\frac{9}{14}\)
\(\frac{-1}{1}.\frac{20}{5}< x< \frac{-1}{5}.\frac{3}{2}\)
\(\frac{-20}{5}< x< \frac{-3}{10}\)
\(\frac{-40}{10}< x< \frac{-3}{10}\)
\(\Rightarrow Z\in\left\{-4;-5;-6;-7;-8;-9;-10;...;-39\right\}\)
Câu 9
a) 2/15 + (-3/5)
= 2/15 - 3/5
= 2/15 - 9/15
= -7/15
b) -5/7 + 3/7 . (-2/9)
= -5/7 - 2/21
= -15/21 - 2/21
= -17/21
c) 5/16 - (7/15 - 3/16) + 17/30
= 5/16 - 7/15 + 3/16 + 17/30
= (5/16 + 3/16) + (17/30 - 14/30)
= 1/2 + 1/10
= 5/10 + 1/10
= 6/10
= 3/5
\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)
\(\frac{-1}{3}:\frac{-5}{6}=\frac{-1}{3}\times\frac{-6}{5}=\frac{2}{5}\)
@muối
(-7)2+(-49).[ -15+(-7)4:73 ]+(-1)2014
=49+(-49).[-15+ 7]+1
=49+(-49).(-8)+1
=49+392+1
=441+1
=442
Bn biết làm câu này hok:
-(x+6)-34=12+3x