Tính bằng cách hợp lí (nếu có thể):
a , ( - 17 + 91 ) - ( 91 - - 17 - 2011 ) b , 4 7 + 5 6 : 5 - 0 , 375 . ( - 2 ) 2 c , ( - 7 11 : 5 12 + - 4 12 : 5 12 ) . 2 - 5 3
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a) ( -17 + |91| ) – ( 91 – |-17| – 2011 )
= ( -17 + 91 ) – ( 91 – 17 – 2011 )
= - 17 + 91 – 91 + 17 + 2011
= ( - 17 + 17 ) + (91 – 91 ) + 2011 = 2011
a) ( -17 + |91| ) – ( 91 – |-17| – 2011 ) = ( -17 + 91 ) – ( 91 – 17 – 2011 )
= - 17 + 91 – 91 + 17 + 2011 = ( - 17 + 17 ) + (91 – 91 ) + 2011 = 2011
a) \(\left(-17+\left|91\right|\right)-\left(91-\left|-17\right|-2011\right)\)
\(=\left(-17+91\right)-\left(91-17-2011\right)\)
\(=74-\left(74-2011\right)\)
\(=74-74+2011\)
\(=0+2011\)
\(=2011\)
b) \(\dfrac{4}{7}+\dfrac{5}{6}:5-0,375.\left(-2\right)^2\)
\(=\dfrac{4}{7}+\dfrac{1}{6}-\dfrac{3}{8}.4\)
\(=\dfrac{24}{42}+\dfrac{7}{42}-\dfrac{3}{2}\)
\(=\dfrac{31}{42}-\dfrac{63}{42}\)
\(=\dfrac{-16}{21}\)
c) \(\left(\dfrac{-17}{11}:\dfrac{5}{12}+\dfrac{-4}{12}:\dfrac{5}{12}\right).2.\dfrac{\left|-5\right|}{3}\)
\(=\left(\dfrac{-17}{11}+\dfrac{-4}{12}\right):\dfrac{5}{12}.\dfrac{2.\left|-5\right|}{3}\)
\(=\left(\dfrac{-204}{132}+\dfrac{-44}{132}\right):\dfrac{5}{12}.\dfrac{2.5}{3}\)
\(=\dfrac{-62}{33}:\dfrac{5}{12}.\dfrac{10}{3}\)
\(=\dfrac{-248}{55}.\dfrac{10}{3}\)
\(=\dfrac{-496}{33}\)
a) − 3 8 . 2 5 + − 3 8 . 14 5 = − 3.2 8.5 + − 3.14 8.5 = − 3 20 + − 21 20 = − 24 20 = − 6 5 .
b) − 17 + 91 − 91 − − 17 − 2019 = − 17 + 91 − 91 − 17 − 2019 = − 17 + 91 − 91 + 17 + 2019 = − 17 + 17 + 91 − 91 + 2019 = 2019 ,
a/=(74-(-1937)1)
=74-(-1937)
=2011
b/=4/7+5/6:5-3/8*(-4)
=4/7+1/6-(-3/2)
=31/42-(-3/2)
=47/21
minh chi biet bay nhieu
a) 105*x-20-18-16-...-2=19+17+15+...+3+1
105*x=1+2+3+4+...+20
105*x=\(\frac{\left(20+1\right)x20}{2}\)
105*x=210
x=2
Vậy x = 2
b) 1-6+11-16+21-26+...+91-96+101
=101-96+91-86+...+21-16+11-6+1
=(101-96)+(91-86)+...+(21-16)+(11-6)+1
=5+5+...+5+5+1 ( có (101-6):5+1);2=10 số 5)
=5x10+1=51
a)105xX-20-18-16-...-2=19+17+15+...+3+1
105xX-(20+18+16+...+2)=19+17+15+...+3+1
105xX-110=100
105xX=100+110
105xX=210
X=210:105
X=2
a> 18.17-3.6.7
= 18.17-18.7
= 18 ( 17-7)
= 18.10 = 180
đi giải tiếp