Câu 1: Thực hiện phép tính bằng cách hợp lí nhất
a) 2012 - (304 +2012 ) + (2013 + 304)
b) 9^14.25^5.8^7/18^12.625^3.24^3
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2012-304-2012+2013+304
=(2012-2012)+(304-304)+2013
=0+0+2013
=2013
20112-(304+2012)+(2013+304)
=20112-304-2012+2013+304
=20112+(-2012+2013)+(-304+304)
=20112+1+0=20113
\(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}=\frac{\left(3^2\right)^{14}.25^5.\left(2^3\right)^7}{2^{12}.\left(3^2\right)^{12}.\left(25^2\right)^3.\left(2^3\right)^3.3^3}=\)\(\frac{3^{28}.25^5.2^{21}}{2^{12}.2^9.3^{24}.3^3.25^6}=\frac{3^{28}.25^5.2^{21}}{2^{21}.3^{27}.25^6}\)\(=\frac{3}{25}\)
\(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}\)
\(=\frac{\left(3^2\right)^{14}.\left(5^2\right)^5.\left(2^3\right)^7}{\left(2.3^2\right)^{12}.\left(5^4\right)^3.\left(2^3.3\right)^3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{2^{12}.3^{24}.5^{12}.2^9.3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{2^{21}.3^{25}.5^{12}}\)
\(=\frac{3^3.1.1}{1.1.5^2}\)
\(=\frac{27}{25}\)
Ta có: \(\dfrac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}\)= \(\dfrac{9^{14}.25^5.8^7}{9^{12}.2^{12}.\left(25^2\right)^3.8^3.3^3}\)=\(\dfrac{9^{12}.9^2.25^5.8^7}{9^{12}.2^{12}.25^6.8^3.3^3}\)
= \(\dfrac{9^{12}.3^4.25^5.8^7}{9^{12}.\left(2^{12}.8^3\right).25^5.25.3^3}\)=\(\dfrac{9^{12}.3^3.3.25^5.8^7}{9^{12}.8^7.25^5.25.3^3}\)=\(\dfrac{\left(9^{12}.3^3.25^5.8^7\right).3}{\left(9^{12}.3^3.25^5.8^7\right).25}\)
=\(\dfrac{3}{25}\)
( Có một vài bước mik làm tắt bặn nhé!)
a,999/2610=111/290
b,374/506=17/23
c,3600-75/8400-175=3/7
d,9^14.25^5.8^7/18^12.625^3.24^3=3/25
a, Ta có:999/2610=111/290
b, Ta có:374/506=17/2
c,Ta có:3600-75/8400-175=48.75-75/48.175-175=75.(48-1)/175.(48-1)=75/175=3/7
d, Ta có:(3^2)^14.(5^2)^5.(2^3)^7/(2.3^2)^12.(5^4)^3.(2^3.3)^3
=3^28.5^10.2^21/2^12.3^24.5^12.2^9.3^3
=3^28.5^10.2^21/2^21.3^27.5^12
=3/5^2=3/25
1 . 2 . 3 . ...... 2012 . ( 2013 - 1 - 2012 )
1 . 2 . 3 ..........2012 . ( 0 ) = 0
1.2.3...2013-1.2.3...2012-1.2.3...20122= (1.2.3...2013-1.2.3...2012) - 1.2.3...20122 = [1.2.3...2012(2013-1)] - 1.2.3...20122 = 1.2.3...2012.2012 - 1.2.3...20122 = 1.2.3...20122 - 1.2.3...20122 = 0
a) 2012 - ( 304 + 2012 ) + ( 2013 + 304 )
= 2012 - 304 - 2012 + 2013 + 304
= 2012 + ( - 304 ) + ( - 2012 ) + 2013 + 304
= [ 2012 + ( - 2012 ) ] + [ ( - 304 ) + 304 ] + 2013
= 0 + 0 + 2013
= 2013
b) \(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}\)
\(=\frac{\left(3^2\right)^{14}.\left(5^2\right)^5.\left(2^3\right)^7}{\left(3^2.2\right)^{12}.\left(5^4\right)^3.\left(2^3.3\right)^3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{3^{24}.2^{12}.5^{12}.2^9.3^3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{3^{27}.5^{12}.2^{21}}\)
\(=\frac{3}{5^2}=\frac{3}{25}\)
a) 2012 - ( 304 + 2012 ) + (2013 + 304 )
= 2012 - 304 +2012 + 2013 + 304
= ( 2012 - 2012 ) + ( 304 + 304 ) + 2013
= 0 + 608 + 2013
= 2621
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