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123.456+123.789-1245.23
=123.(456+789)-1245.23
=123.1245-1245.23
=1245.(123-23)
=1245.100
=124500
=123.(456+789)-1245.23
=123.1245-1245.23
=1245.(123-23)
=1245.100
=124500
![](https://rs.olm.vn/images/avt/0.png?1311)
a)Ta có\(123\times456+123\times789+1245\times23\)
\(=123\left(456+789\right)+1245.23\)
\(=123.1245+1245.23\)
\(=1245\left(123+23\right)\)
\(=1245.146\)
\(=181770\)
b)\(2^9:16^2+81^5:3^{18}-125^7:625^5\)
\(=2^9:\left(2^4\right)^2+\left(3^4\right)^5:3^{18}-\left(5^3\right)^7:\left(5^4\right)^5\)
\(=2^9:2^8+3^{20}:3^{18}-5^{21}:5^{20}\)
\(=2+3^2-5\)
\(=2+9-5\)
\(=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 12^7 : 6^7 = (12 : 6)^7 = 2^7 = 128.
b,27^5 : 81^3 = (3^3)^5 : (3^4)^3 = 3^15 : 3^12 = 3^15 - 12 = 33 = 27
c,18^3 : 9^3 = (18 : 9)^3 = 2^3 = 8.
d, 125^3 : 2^4 = (5^3)^3 : (52)4 = 5^9 : 5^8 = 5^9 - 8 = 5.
a,vì có cùng số mũ =>12:6=2
b,ta có 125=(5^3)^5,25^3=(5^2)^3=>5^15:5^6=5^9
c,ta có 27^5=(3^3)^5,81^3=(3^4)^3=>3^15:3^12=3^3
d, vì có cùng số mũ =>18:9=2
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a)\(\frac{-5}{18}+\frac{32}{45}-\frac{9}{10}\)
\(=\frac{-25}{90}+\frac{64}{90}-\frac{81}{90}\)
\(=-\frac{42}{90}=-\frac{7}{15}\)
b)\(\frac{3}{4}-\left(-\frac{5}{8}\right)+\frac{9}{4}-\frac{3}{16}\)
\(=\frac{3}{4}+\frac{5}{8}+\frac{9}{4}-\frac{3}{16}\)
\(=\frac{12}{16}+\frac{10}{16}+\frac{36}{16}-\frac{3}{16}\)
\(=\frac{58}{16}=\frac{29}{8}\)
c) \(\frac{11}{125}-\frac{17}{18}-\frac{5}{7}+\frac{4}{9}+\frac{17}{14}=\frac{11}{125}\)
d) \(\frac{-2}{5}-\frac{3}{10}-\left(-\frac{1}{2}\right)\)
\(=-\frac{2}{5}-\frac{3}{10}+\frac{1}{2}\)
\(=-\frac{4}{10}-\frac{3}{10}+\frac{5}{10}\)
\(=-\frac{2}{10}=-\frac{1}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1, \(81\cdot27^3\cdot243^5=3^4\cdot3^9\cdot3^{25}=3^{38}\)
2,\(25^4\cdot125^3\cdot625^7=5^8\cdot5^9\cdot5^{28}=5^{45}\)
3,
\(16^3\cdot8^9\cdot64^5\cdot1024=2^{12}\cdot2^{27}\cdot2^{30}\cdot2^{10}=2^{79}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 1 - 3 + 5 - 7 + 9 - 11
= (1 - 3) + (5 - 7) + (9 - 11)
= (-2) + (-2) + (-2)
= -6
b) -14 - 16 - 18 - ... - 92
= - (14 + 16 + 18 + .... + 92)
Áp dụng công thức tính dãy số ta có :
14 + 16 + 18 + .... + 92 = 2120
= -2120
c) 15 + 18 + 21 + .... + 63 + 66 + 70
= (15 + 18 + 21 + ..... + 66) + 70
Áp dụng công thức tính dãy số ta có :
15 + 18 + ..... + 66 = 729
= 729 + 70
= 8799
d) 2 - 3 + 4 - 5 + 6 - 7 + 8 - 9 + 10
= (2 - 3) + (4 - 5) + (6 - 7) + (8 - 9) + 10
= (-1) + (-1) + (-1) + (-1) + 10
= 6
29 : 162 + 815 : 318 - 1257 : 6255
= 29 : ( 24 )2 + ( 34 )5 : 318 - ( 53 )7 : ( 54 )5
= 29 : 28 + 320 : 318 - 521 : 520
= 2 + 32 - 5
= 2 + 9 - 5
= 6
16^2=(2^4)^2=2^8
81^5=(3^4)^5=3^20
125^7=(5^3)^7=5^21
625^5=(5^4)^5 =5 ^20
TA CÓ 2^9/ 16^1+81^4/3^18-125^7/625^5
=2^9/2^8+3^20/3^18-5^21/5^20
=2+3 ^ 2 -5
=2+9-5
=11-5=6