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− 2018 + − 21 + 75 + 2018 = − 2018 + − 21 + 75 + 2018 = − 2018 + 2018 + − 21 + 75 = 0 + 54 = 54.
a) 7 23 + 16 23 + − 5 9 + − 4 9 + − 5 8 = − 5 8
b) − 2 9 + − 3 4 + − 1 36 + 1 3 + 3 5 + 1 5 = 0
a) 7 23 + − 10 18 + − 4 9 + 16 23 + − 5 8 = 7 23 + 16 23 + − 5 9 + − 4 9 + − 5 8 = − 5 8
b) 1 3 + − 3 4 + 3 5 + − 1 36 + 1 15 + − 2 9 = 1 3 + 3 5 + 1 15 + − 3 4 + − 1 36 + − 2 9 = 0
Bài 1:
a: \(\dfrac{25}{42}-\dfrac{20}{63}=\dfrac{75-40}{126}=\dfrac{35}{126}=\dfrac{5}{18}\)
b: \(\dfrac{9}{20}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{135}{300}-\dfrac{52}{300}-\dfrac{50}{300}=\dfrac{33}{300}=\dfrac{11}{100}\)
a ) 4 7 + 1 7 + 3 7 = 8 7 b ) 4 7 + − 3 7 + − 1 2 + 1 2 = 1 7
c ) − 27 10 + − 3 10 + 1 4 + 5 4 + 13 2 = − 3 + 3 2 + 13 2 = 5 d ) 8 5 + 7 5 + − 11 4 + − 9 4 + − 7 20 = 3 − 5 + − 7 20 = − 47 20 e ) 7 5 + − 1 15 + − 11 3 + 11 2 + 1 6 + ( − 2 ) = 4 3 + 2 + ( − 2 ) = 4 3
a) \(\left(-25\right).5.\left(-4\right).2\)
\(=\left[\left(-25\right).\left(-4\right)\right].\left(2.5\right)\)
\(=100.10=1000\)
b) \(\left(-456\right)-\left(67-456\right)\)
\(=-456-67+456\)
\(=\left(456-456\right)-67\)
\(=67\)
a ) 5 4 9 − 9 7 12 − 4 5 9 = 5 4 9 + 4 5 9 − 9 7 12 = 10 − 9 7 12 = 5 12 .
b ) 8 1 3 + 7 , 8 + 5 2 3 − 1 , 8. = 8 1 3 + 5 2 3 + 7 , 8 − 1 , 8 = 14 + 6 = 20
254 - 49 - 75 + 254 - 175 + 549
= ( 549 - 49 ) - ( 175 + 75 ) + 254 + 254
= 500 - 250 + 254 + 254
= 758