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B) 2x + (-416) - (231 - 416 )
= 2x - 416 - 231 + 416
= 2x - ( 416 +231 - 416 )
= 2x - 231
D) 211-(123-x)+(123-211)
= 211 - 123 + x + 123 - 211
= ( 211 - 123 +123 - 211 )+ x
= 0+ x
= x
b) 2x + (-461) - (231 - 416)
= 2x - 461 - (231 - 416)
= 2x - 461 + 185
= 2x - 276
d) 211 - (123 - x) + (123 - 211)
= 211 - 123 + x + 123 - 211
= (211 - 211) + (-123 + 123) + x
= 0 + 0 + x
= x
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a: \(A=\dfrac{63-48-70}{84}:\dfrac{-3\cdot84+4\cdot60+5\cdot70}{840}\cdot\dfrac{1-14}{12}\)
\(=\dfrac{-55}{84}\cdot\dfrac{840}{338}\cdot\dfrac{-13}{12}=\dfrac{55}{1}\cdot\dfrac{10}{338}\cdot\dfrac{13}{12}=\dfrac{275}{156}\)
b: \(=-234\cdot123+123\cdot4356-123\cdot2312+234\cdot123-234\cdot2312+2312\cdot234+2312\cdot123\)
\(=123\cdot4356-123\cdot2312+123\cdot2312=123\cdot4356=535788\)
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\(\left(\frac{377}{-213}-\frac{123}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-213}-\frac{123}{89}+\frac{34}{791}\right).0\)
\(=0\)
(377/-213 - 123/89 +34/791 ). (1/6 - 1/8 - 1/24).
=(377/-213 - 123/89+34/791). 0
= 0
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\(\dfrac{3}{4}-\left[\left(-\dfrac{3}{5}\right)-\left(\dfrac{1}{12}+\dfrac{2}{4}\right)\right]\\ =\dfrac{3}{4}-\left[\left(-\dfrac{3}{5}\right)-\left(\dfrac{1}{12}+\dfrac{6}{12}\right)\right]\\ =\dfrac{3}{4}-\left[\left(-\dfrac{3}{5}\right)-\dfrac{7}{12}\right]\\ =\dfrac{3}{4}-\left[\left(-\dfrac{36}{60}\right)-\dfrac{35}{60}\right]\\ =\dfrac{3}{4}-\left(-\dfrac{71}{60}\right)\\ =\dfrac{3}{4}+\dfrac{71}{60}\\ =\dfrac{35}{60}+\dfrac{71}{60}\\ =\dfrac{106}{60}\\ =\dfrac{53}{30}\)
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\(-\dfrac{6}{7}.\dfrac{21}{12}\\ =-\dfrac{126}{84}\\ =-\dfrac{63}{42}\\ =-\dfrac{31}{14}\)
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\(\left(-5\right).\left(-\dfrac{6}{20}\right)\\ =\dfrac{\left(-5\right).\left(-6\right)}{20}\\ =\dfrac{30}{20}\\ =\dfrac{3}{2}\)
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1 + 4 = 5
2 + 5 = 12 ( 2 + 5 + 5 = 12)
3 + 6 = 21 (3 + 6 + 12 = 21)
8 + 11 = 40 ( 8 + 11 + 21= 40)
Quy luật Cộng thêm kết quả của dãy số ở trên
`6,(123) =` \(\dfrac{2039}{333}\)
\(6,\left(123\right)=6+0,\left(123\right)=6+\dfrac{123}{999}=\dfrac{2039}{333}\)