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e
, 11-12 +13-14 +15-16 +17-18+19-20
= (11-12) +(13-14) +(15-16) +(17-18) +(19-2)
= - 1 . 4 + (19-2)
= 4 + 17
= 21
a) 12 : { 400 : [ 500 - ( 125 + 25 . 7 )]}
= 12 : { 400 : [ 500 - ( 125 + 175 )]}
= 12 : { 400 : [ 500 - 300 ]}
= 12 : { 400 : 200 }
= 12 : 2
= 6
b) 5 . 22 - 18 : 3
= 110 - 6
= 104
c) 18 : 3 + 182 + 3 . ( 51 : 17 )
= 6 + 182 + 3.3
= 6 + 182 + 9
= 197
d) 25.8 - 12.5 + 170 : 17 - 8
= 1000 - 60 + 10 - 8
= 940 + 10 - 8
= 940 + 2
= 942
\(a,\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b,\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14+\left(-15\right)}{21}=\dfrac{-29}{21}\\ c,\dfrac{1}{2}-\dfrac{-1}{2}-\dfrac{1}{3}=\dfrac{3+3-2}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)
\(a.\dfrac{4}{28}+\dfrac{12}{36}=\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b.\dfrac{-12}{18}+\dfrac{-15}{21}=\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14}{21}+\dfrac{-15}{21}=\dfrac{-29}{21}\\ c.\dfrac{14}{28}+\dfrac{16}{32}-\dfrac{17}{51}=\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{17}{51}=1-\dfrac{17}{51}=\dfrac{2}{3}\)
Ta có:
A=1718+11719+1A=1718+11719+1
⇒17A=1719+1+161719+1⇒17A=1719+1+161719+1
⇒17A=1+161719+1⇒17A=1+161719+1
B=1717+11718+1B=1717+11718+1
⇒17B=1718+1+161718+1⇒17B=1718+1+161718+1
⇒17B=1+161718+1⇒17B=1+161718+1
Vì 161719+1<161718+1⇒17A<17B161719+1<161718+1⇒17A<17B
⇒A<B⇒A<B
Vậy A<B
Câu 1 :\(289:17-324:18+18:3\)
\(=17-18+6\)
\(=-1+6\)
\(=5\)
Câu 2 : \(18.3-182+3.\left(51:17\right)\)
\(=18.3-182+3.3\)
\(=54-182+9\)
\(=-128+9\)
\(=-119\)
(-58)+(-27)+18+24+51+(-17)
=(-58)+(-27)+(-17)+93
=(-85)+(-17)+93
=(-102)+93
=-9
giải ra ko ghi kết quả
\(-\frac{-12}{17}.-\frac{-51}{18}\)
\(=\frac{12}{17}.\frac{51}{18}\)
=\(\frac{12.51}{17.18}=\frac{3.2.2.17.3}{17.3.3.2}\)
\(=2\)