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17 . 85 + 17 . 15 + 300
= 17 . ( 85 + 15 ) + 300
= 17 . 100 + 300
= 1 700 + 300
= 1 400
72 . 121 + 27 . 121 + 121
= 121 . ( 72 + 27 + 1 )
= 121 . 100
= 12 100
32 . 39 + 52 . 21 - 12 . 39 + 21 . 48
= 39 . ( 32 - 12 ) + 21 . ( 52 + 48 )
= 39 . 20 + 21 . 100
= 780 + 2 100
= 9 900
a.=17*(85+15)+300
=17*100+300
=1700+300=2000
b.=121*(72+27+1)
=121*100=12100
c.chịu
a)\(3.5^2-16:2^2\)
=\(3.25-16:4\)
=\(75-4=71\)
b)\(2^3.17-2^3.14\)
=\(8.17-8.14\)
\(=8\left(17-14\right)\)
\(=8.3=24\)
c)\(15.141+59.15\)
=\(15\left(141+59\right)\)
\(=15.200\)=3000
d)17.85+15.17-120
\(=17\left(85+15\right)-120\)
=\(17.100-120\)
=\(170-120=50\)
e)\(20+[30-\left(5-1\right)^2]\)
\(=20+[30-\left(4\right)^2]\)
\(=20+\left(30-16\right)\)
\(=20+14=34\)
1/ Bg
\(\frac{21^4}{27.\left(-343\right)}\)= \(\frac{\left(3.7\right)^4}{3^3.\left(-7\right)^3}\)
= \(\frac{3^4.7^4}{3^3.\left(-7\right)^3}\)
= \(\frac{3.\left(-7\right)}{1.1}\)
= 3.(-7)
= -21
2/ Bg
Ta có: \(\frac{a}{4}=\frac{b}{5}=\frac{c}{2}\)và a + b - c = 21 (a, b, c thuộc Z)
Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\frac{a}{4}=\frac{b}{5}=\frac{c}{2}=\frac{a+b-c}{4+5-2}=\frac{21}{7}\)= 3
=> a = 3.4 = 12
=> b = 3.5 = 15
=> c = 3.2 = 6
Vậy a = 12, b = 15 và c = 6
-(127+38-21)-(121-27+48)+50
=-127-38+21-121+27-48+50
=(-127+27)-(38+48)+(21-121)+50
=-100-86-100+50
=-(100+100+86)+50
=-286+50
=-236
-39+(193-127+96)-(193+196-127)
=-39+193-127+96-193-196+127
=-39+(193-193)-(127+127)+(96-196)
=-39-100
=-139
\(125\%\cdot\left(-\frac{1}{2}\right)^2\div\left(1\frac{5}{6}-1,5\right)+2016^0\)
\(=\frac{125}{100}\cdot\frac{1}{4}\div\left(\frac{11}{6}-\frac{3}{2}\right)+1\)
\(=\frac{5}{4}\cdot\frac{1}{4}\div\left(\frac{11}{6}-\frac{9}{6}\right)+1\)
\(=\frac{5}{16}\div\frac{2}{6}+1\)
\(=\frac{15}{16}+1=\frac{31}{16}\)
\(125\%.\left(\frac{-1}{2}\right)^2:\left(1\frac{5}{6}-1,5\right)+2016^0\)
\(=\frac{125}{100}.\frac{1}{4}:\left(\frac{11}{6}-\frac{3}{2}\right)+1\)
\(=\frac{5}{16}:\left(\frac{11}{6}-\frac{9}{6}\right)+1\)
\(=\frac{5}{16} :\frac{1}{3}+1\)
\(=\frac{5}{16} .\frac{3}{1}+1\)
\(=\frac{15}{16}+1\)
\(=\frac{31}{16}\)
a) 17. 85 + 15 . 17 = 300
= 17. 9 85 = 15) + 300
= 2000
b) 72. 121 + 27 .121 = 121
= 121 . ( 72 + 27 = 1)
= 12100
c) 32. 39 + 52 . 21 - 12 . 39 + 21 . 48
= ( 32 - 12).39 + 21. ( 52 + 48)
= 2880
d) 47 - ( 45.24 - 52.12) : 14
= 47 - ( 45 . 16 - 25.12) : 14
= 17
e) 102 - 60 : ( 54 : 52 - 3. 5)
= 100 - 60 : ( 25 - 15)
= 100 - 6
= 94