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Bài 1:
a, 386-287 -386 -13
= (386-386) -287-13
= 0 -300
=-300
b, =332-681 -232+431
= (332 -232) +(431-681)
= 100 - 250
= -150
Bài 2
a, = 27+65+ 364-27-65
= (27-27) +(65-65) +364
= 0+0+ 364
=364
b, = 42-69+17 -42-17
= (42-42) + (17-17) -69
= -69
chúc bạn học tốt nha!
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a/ 525.5:225+|-125|
=525.5:225+125
=525.51:225+53
=525+1-25+3
=54
b/232:[315-(230+8)]
=232:[315-230-8]
=232:77
= phần b đề sai
c/(-1732)+7376-(-1998)+(-2546)
=-1732+7376+1998-2546
=7642-2546
=5096.
a ) 525 . 5 : 525 + l - 125 l
= 525 . 51 : 525 + 125
= 525+1-25+3
= 54
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12.25+29.25+59.25
=25.(12+29+59)
=25.100
=2500.
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\(\frac{25}{72}+\frac{25}{90}+\frac{25}{110}+...+\frac{25}{9900}\)
= \(25.\left(\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+...+\frac{1}{9900}\right)\)
= \(25.\left(\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+...+\frac{1}{99.100}\right)\)
= \(25.\left(\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+...+\frac{1}{99}-\frac{1}{100}\right)\)
= \(25.\left(\frac{1}{8}-\frac{1}{100}\right)\)
= \(25.\frac{23}{200}\)
= \(\frac{23}{8}\)
-332.-25-25.232
=25(332-232)
=25.100
=2500
(-332) . (-25 ) - 25 . 232
=[ (-332).(-25) ] - 25.232
= 332 . 25 - 25 . 232
= 25 . (332 - 232 )
= 25 . 100
= 2500