Tính hợp lý:\(\dfrac{3}{5}\)-(\(2\dfrac{3}{4}\)+\(2\dfrac{3}{5}\))
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a) \(\dfrac{-3}{5}+\dfrac{7}{21}+\dfrac{-4}{5}+\dfrac{7}{5}\)
\(=\left(-\dfrac{3}{5}+\dfrac{-4}{5}+\dfrac{7}{5}\right)+\dfrac{7}{21}\)
\(=0+\dfrac{7}{21}\)
\(=\dfrac{7}{21}\)
b) `-3/17 + ( 2/3 + 3/17)`
` = -3/17 + 2/3 + 3/17`
` = 2/3 + ( -3/17 +3/17)`
` = 2/3 + 0`
` = 2/3`
c)
` -5/21 + ( -16/21 +1)`
\(=\dfrac{-5}{21}+\dfrac{-16}{21}+1\)
\(=\left(\dfrac{-5}{21}+\dfrac{-16}{21}\right)+1\)
\(=-1+1=0\)
1) = (8/31 + 23/31)+ ( -12/25+-13/25) = 1 + (-1) = 0
2) = 1/2 +3/4 -3/4 + 4/5 = 1/2 +4/5 = 13/10
3)= ( 7/3 x 15/21) x ( -5/2 x 4/-5 ) = ( 7/3 x 5/7 ) x 2 = 5/3 x 2 = 10/3
4) = 1/4 + 3/4 x -7/6 = 1/4 + -7/8 = -5/8
5)= 3/29 x 29/3 - 1/5 x 29/3 = 1 x 29/15 = 29/15
6)= 5/7 x ( 5/11 + 2/11 - 14/11) = 5/7 x -7/11 = -5 /11
7) = 11/12 x -1/8 + 11/12 x -3/16 - 11/12 = 11/12 x ( -1/8 + -3/16 - 1) = 11/12 x -21/16 = -77/64 ( mk ko chắc , bạn ấn máy tính để thử lại )
8) = 203/20 - 7/4 + 41/13 = 198/20 + 41/13 = 99/10 + 41/13 = 1697/130 ( câu này cứ lỏ lỏ kiểu gì ý :v )
1) = (8/31 + 23/31)+ ( -12/25+-13/25) = 1 + (-1) = 0
2) = 1/2 +3/4 -3/4 + 4/5 = 1/2 +4/5 = 13/10
3)= ( 7/3 x 15/21) x ( -5/2 x 4/-5 ) = ( 7/3 x 5/7 ) x 2 = 5/3 x 2 = 10/3
4) = 1/4 + 3/4 x -7/6 = 1/4 + -7/8 = -5/8
5)= 3/29 x 29/3 - 1/5 x 29/3 = 1 x 29/15 = 29/15
6)= 5/7 x ( 5/11 + 2/11 - 14/11) = 5/7 x -7/11 = -5 /11
7) = 11/12 x -1/8 + 11/12 x -3/16 - 11/12 = 11/12 x ( -1/8 + -3/16 - 1) = 11/12 x -21/16 = -77/64 ( mk ko chắc , bạn ấn máy tính để thử lại )
8) = 203/20 - 7/4 + 41/13 = 198/20 + 41/13 = 99/10 + 41/13 = 1697/130 ( câu này cứ lỏ lỏ kiểu gì ý :v )
\(\dfrac{3}{7}.\left(-\dfrac{2}{5}\right).2\dfrac{1}{3}.20.\dfrac{19}{72}\)
\(=\dfrac{3}{7}.\left(-\dfrac{2}{5}\right).\dfrac{7}{3}.20.\dfrac{19}{72}\)
\(=\left(-\dfrac{6}{35}\right).\dfrac{7}{3}.20.\dfrac{19}{72}\)
\(=\left(-\dfrac{2}{5}\right).20.\dfrac{19}{72}\)
\(=\left(-8\right).\dfrac{19}{72}\)
\(=-\dfrac{19}{9}\)
\(=\dfrac{102}{5}\cdot\dfrac{6}{5}-\dfrac{107}{3}\cdot\dfrac{6}{5}-\dfrac{3}{4}\)
\(=\dfrac{6}{5}\cdot\dfrac{-229}{15}-\dfrac{3}{4}\)
\(=\dfrac{-458}{25}-\dfrac{3}{4}=-\dfrac{1907}{100}\)
= 102/5 x 6/5 - 107/3 x 6/5 - 3/4
= 6/5 x ( 102/5 - 107/3 ) - 3/4
= 6/5 x -229/15 - 3/4
= -458/25 - 3/4
= -1907/100
\(=\dfrac{-3}{4}-\dfrac{1}{2}-\dfrac{3}{4}+\dfrac{5}{8}=\dfrac{-6}{4}+\dfrac{5}{8}-\dfrac{1}{2}=-2+\dfrac{5}{8}=\dfrac{-16+5}{8}=-\dfrac{11}{8}\)
\(a,\left(31\dfrac{6}{13}+5\dfrac{9}{41}\right)-36\dfrac{6}{13}\\ =\left(31-36\right)+\left(\dfrac{6}{13}-\dfrac{6}{13}\right)+5\dfrac{9}{41}\\ =-5+0+5\dfrac{9}{41}\\ =\left(-5+5\right)+\dfrac{9}{41}=\dfrac{9}{41}\)
\(b,\dfrac{5}{3}+\left(-\dfrac{2}{7}\right)-\left(-1,2\right)\\ =\dfrac{5}{3}-\dfrac{2}{7}+\dfrac{6}{5}\\ =\dfrac{5.35-2.15+6.21}{105}=\dfrac{271}{105}\\ c,0,25+\dfrac{3}{5}-\left(\dfrac{1}{8}-\dfrac{2}{5}+1\dfrac{1}{4}\right)=\dfrac{1}{4}+\dfrac{3}{5}-\dfrac{1}{8}+\dfrac{2}{5}-1\dfrac{1}{4}\\ =\left(-1\dfrac{1}{4}+\dfrac{1}{4}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)-\dfrac{1}{8}=-1+1-\dfrac{1}{8}=-\dfrac{1}{8}\)
a) (31 6/13 + 5 9/41) - 36 6/13
= 409/13 + 214/41 - 474/13
= (409/13 - 474/13) + 214/41
= -5 + 214/41
= 9/41
b) 5/3 + (-2/7) - (-1,2)
= 5/3 - 2/7 + 6/5
= 29/21 + 6/5
= 271/105
c) 0,25 + 3/5 - (1/8 - 2/5 + 1 1/4)
= 1/4 + 3/5 - 1/8 + 2/5 - 5/4
= (1/4 - 5/4) + (3/5 + 2/5) - 1/8
= -1 + 1 - 1/8
= -1/8
\(\dfrac{2^{12}\cdot3^5-4^6\cdot9^2}{\left(2^2\cdot3\right)^6}-\dfrac{5^{10}\cdot7^3-25^5\cdot49^2}{\left(125\cdot7\right)^3+5^9\cdot14^3}\\ =\dfrac{2^{12}\cdot3^5-\left(2^2\right)^6\cdot\left(3^2\right)^2}{2^{12}\cdot3^6}-\dfrac{5^{10}\cdot7^3-\left(5^2\right)^5\cdot\left(7^2\right)^2}{\left(5^3\cdot7\right)^3+5^9\cdot\left(2\cdot7\right)^3}\\ =\dfrac{2^{12}\cdot3^5-2^{12}\cdot3^4}{2^{12}\cdot3^6}-\dfrac{5^{10}\cdot7^3-5^{10}\cdot7^4}{5^9\cdot7^3+5^9\cdot2^3\cdot7^3}\\ =\dfrac{2^{12}\cdot3^4\left(3-1\right)}{2^{12}\cdot3^6}-\dfrac{5^{10}\cdot7^3\left(1-7\right)}{5^9\cdot7^3\left(1+2^3\right)}\\ =\dfrac{2}{9}-\dfrac{-6}{1+8}=\dfrac{2}{9}+\dfrac{6}{9}=\dfrac{8}{9}\)
\(\dfrac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6}-\dfrac{5^{10}.7^3-25^5.49^2}{\left(125.7\right)^3+5^9.14^3}\\ =\dfrac{2^{12}.3^5-2^{12}.3^6}{2^{12}.3^6}-\dfrac{5^{10}.7^3-5^{10}.7^4}{5^9.7^3+5^9.2^3.7^3}\\ =\dfrac{2^{12}.3^5.\left(1-3\right)}{2^{12}.3^6}-\dfrac{5^{10}.7^3.\left(1-7\right)}{5^9.7^3.\left(1+2^3\right)}\\ =\dfrac{2^{12}.3^5.\left(-2\right)}{2^{12}.3^6}-\dfrac{5^{10}.7^3.\left(-6\right)}{5^9.7^3.9}\\ =\dfrac{-2}{3}-\dfrac{5.\left(-6\right)}{9}\\ =\dfrac{-2}{3}+\dfrac{30}{9}\\ =\dfrac{8}{3}\)
\(=\left(\dfrac{2}{5}+\dfrac{-2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}-\dfrac{5}{2}\right)\\ =0+0=0\)
\(\dfrac{2}{5}+\dfrac{5}{4}+\left(\dfrac{-2}{5}+\dfrac{5}{4}\right)-\dfrac{5}{2}\\ =\dfrac{2}{5}+\dfrac{5}{4}-\dfrac{2}{5}+\dfrac{5}{4}-\dfrac{5}{2}\\ =\left(\dfrac{2}{5}-\dfrac{2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}\right)-\dfrac{5}{2}\\ =0+\dfrac{10}{4}-\dfrac{5}{2}\\ =\dfrac{5}{2}-\dfrac{5}{2}\\ =0\)
1, \(\dfrac{-3}{5}:\dfrac{7}{5}-\dfrac{3}{5}:\dfrac{7}{5}+2\dfrac{3}{5}\)
\(=\left(\dfrac{-3}{5}-\dfrac{3}{5}\right):\dfrac{7}{5}+\dfrac{13}{5}\)
\(=\dfrac{-6}{5}:\dfrac{7}{5}+\dfrac{13}{5}\)
\(=\dfrac{-6}{7}+\dfrac{13}{5}\\ =\dfrac{61}{35}\)
2, \(0,75-\left(2\dfrac{1}{3}+0,75\right)+3^2\cdot\left(-\dfrac{1}{9}\right)\)
\(=0,75-\dfrac{37}{12}+9\cdot\left(-\dfrac{1}{9}\right)\)
\(=-\dfrac{7}{3}+\left(-1\right)\\ -\dfrac{10}{3}\)
=3/5 -( 11/4+13/5)
=3/5 -11/4-13/5
=3/5-13/5-11/4
=(-2)-11/4
=-19/4
@kudoshin