a) 135 + (-2) . 14 -135 + 28
b) -18 . 2 +18 . (-6) + (-18) . 3
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\(a)135+\left(-2\right).14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=135-135+\left(-28\right)+28\)
\(=0+0\)
\(=0\)
\(b)\left(-18\right).2+18.\left(-6\right)+\left(-18\right).3\)
\(=\left(-36\right)+\left(-108\right)+\left(-54\right)\)
\(=\left(-144\right)+\left(-54\right)\)
\(=\left(-198\right)\)
a: \(=\dfrac{54-34}{189-119}=\dfrac{20}{70}=\dfrac{2}{7}\)
b: \(=\dfrac{6+6\cdot4+6\cdot49}{15+15\cdot4+15\cdot49}=\dfrac{6}{15}=\dfrac{2}{5}\)
c: \(=\dfrac{13\left(3-18\right)}{40\left(15-2\right)}=\dfrac{-15}{40}=-\dfrac{3}{8}\)
\(a,31.\left(-18\right)+31.\left(-81\right)-31\)
\(=31\left(-18-81-1\right)\)
\(=31\left(-100\right)\)
\(=-3100\)
\(b,13\left(23+22\right)-3\left(17+28\right)\)
\(=299+286-51-84\)
\(=450\)
\(S=\dfrac{27+4500+135+550.2}{2+4+6+...+14+16+18}\)
\(S=\dfrac{4527+135+1100}{\left(2+18\right).9.2}\)
\(S=\dfrac{4662+1100}{20.9.2}\)
\(S=\dfrac{5762}{90}\)
\(S=\dfrac{2881}{45}\)
`S=(27+4500+135+550.2)/(2+4+6+…+14+16+18)`
`S=(27+4500+135+1100)/((2+18)+(4+16)+…+(8+12)+10)`
`S=((27+135)+(4500+1100))/(20+20+…+20+10)` `(`Có `4` số hạng `20)`
`S=(162+5600)/(20.4+10)`
`S=5762/90`
`S=2881/45`
( 18+29 ) + ( 158-28-18)
=18+29+158-28-18
=29 + ( 18-18) + ( 158-28)
=29+0+130=159
(13-135+49)-(13+49)
=13-135+49-13-49
=(13-13)+(49-49)-135
=0+0+(-135)
=-135
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2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
Đáp án :
a) \(135+\left(-2\right).14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=135-28-135+28\)
\(=135-135+28-28=0\)
b) \(-18.2+18.\left(-6\right)+\left(-18\right).3\)
\(=18.\left(2+6+3\right)=18.11=198\)
a) \(135+\left(-2\right)\cdot14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=\left(135-135\right)+\left[\left(-28\right)+28\right]\)
\(=0+0\)
\(=0\)
b) \(-18\cdot2+18\cdot\left(-6\right)+\left(-18\right)\cdot3\)
\(=-18\cdot2+\left(-18\right).6+\left(-18\right).3\)
\(=-18\cdot\left(2+6+3\right)\)
\(=-18\cdot11\)
\(=-198\)