Phá dấu ngoặc rồi tính:
a)(1x2)3; b)2(6x3);
c)6(2x9); d)(3x8)2.
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a) (56 - 27) - (11 + 28 - 16)
= 56 - 27 - 11 - 28 + 16
= (56 + 16) – (27 + 11 + 28)
= 72 – (38 + 28)
= 72 – 66
= 6
b) 28 + (19 - 28) - (32 - 57)
= 28 + 19 – 28 – 32 + 57
= (28 – 28) + (19 + 57) – 32
= 0 + 76 – 32
= 76 - 32
= 44
a) (56 - 27) - (11 + 28 - 16)
= 56 - 27 - 11 - 28 + 16
= 56 – ( 27 + 11 + 28) + 16
= 56 – 66 + 16
= -10 + 16
= 6
b) 28 + (19 - 28) - (32 - 57)
= 28 + 19 – 28 – 32 + 57
= (28 – 28) + 19 - 32 + 57
= 0 + (-13) + 57
= 44
a) = 29 +37 + 13 +10 - 37 - 13
= 39
b) 79 +32 - 35 - 69 - 12 +75
= 70
a)
\(\begin{array}{l}\left( {\frac{{ - 3}}{7}} \right) + \left( {\frac{5}{6} - \frac{4}{7}} \right)\\ = \left( {\frac{{ - 3}}{7}} \right) + \frac{5}{6} - \frac{4}{7}\\ = \left[ {\left( {\frac{{ - 3}}{7}} \right) - \frac{4}{7}} \right] + \frac{5}{6}\\ =\frac{-7}{7}+\frac{5}{6}\\= - 1 + \frac{5}{6}\\ = \frac{{ - 1}}{6}\end{array}\)
b)
\(\begin{array}{l}\frac{3}{5} - \left( {\frac{2}{3} + \frac{1}{5}} \right)\\ = \frac{3}{5} - \frac{2}{3} - \frac{1}{5}\\ = (\frac{3}{5} - \frac{1}{5}) - \frac{2}{3}\\ = \frac{2}{5} - \frac{2}{3}\\ = \frac{6}{{15}} - \frac{{10}}{{15}}\\ = \frac{{ - 4}}{{15}}\end{array}\)
c)
\(\begin{array}{l}\left[ {\left( {\frac{{ - 1}}{3}} \right) + 1} \right] - \left( {\frac{2}{3} - \frac{1}{5}} \right)\\ = \left( {\frac{{ - 1}}{3}} \right) + 1 - \frac{2}{3} + \frac{1}{5}\\ = \left( {\frac{{ - 1}}{3} - \frac{2}{3}} \right) + 1 + \frac{1}{5}\\ = \frac{-3}{3}+1+\frac{1}{5}\\= - 1 + 1 + \frac{1}{5}\\ = \frac{1}{5}\end{array}\)
d)
\(\begin{array}{l}1\frac{1}{3} + \left( {\frac{2}{3} - \frac{3}{4}} \right) - \left( {0,8 + 1\frac{1}{5}} \right)\\ = 1 + \frac{1}{3} + \frac{2}{3} - \frac{3}{4} - \left( {\frac{4}{5} + 1 + \frac{1}{5}} \right)\\=1+\frac{3}{3}-\frac{3}{4}-(\frac{5}{5}+1)\\ = 1 + 1 - \frac{3}{4} - (1+1)\\ = - \frac{3}{4}\end{array}\).
a)
Cách 1.
\(\begin{array}{l}\left( {4 + 32 + 6} \right) + \left( {10 - 36 - 6} \right)\\ = 4 + 32 + 6 + 10 - 36 - 6\\ = 52 + \left( { - 36} \right) + \left( { - 6} \right)\\ = 52 + \left( { - 42} \right) = 52 - 42 = 10\end{array}\)
Cách 2.
\(\begin{array}{l}\left( {4 + 32 + 6} \right) + \left( {10 - 36 - 6} \right)\\ = 4 + 32 + 6 + 10 - 36 - 6\\ = 36 + 6 + 10 + \left( { - 36} \right) + \left( { - 6} \right)\\ = 36 + \left( { - 36} \right) + 6 + \left( { - 6} \right) + 10\\ = 0 + 0 + 10 = 10\end{array}\)
b) \(\left( {77 + 22 - 65} \right) - \left( {67 + 12 - 75} \right)\)
\(\begin{array}{l} = 77 + 22 - 65 - 67 - 12 + 75\\ = 77 - 67 + 22 - 12 + 75 - 65\\ = 10 + 10 + 10 = 30\end{array}\)
c) \( - \left( { - 21 + 43 + 7} \right) - \left( {11 - 53 - 17} \right)\)
\(\begin{array}{l} = 21 - 43 - 7 - 11 + 53 + 17\\ = 21 - 11 + 53 - 43 + 17 - 7\\ = 10 + 10 + 10 = 30\end{array}\)
a)6
b)36
c)108
d)48