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a) (-385 + 210) + (385 - 217)
= -385 + 210 + 385 - 217
= (-385 + 385) + (210 – 217)
= 0 + (-7) = -7
b) (72 - 1 956) - (-1 956 + 28)
= 72 - 1 956 + 1956 - 28
= ( 1956 – 1956) + ( 72 – 28)
= 0 + 44 = 44.
a.\(\left(258-79\right)-\left(111-90\right)\)
\(=258-79-111+90\)
\(=258+\left(-79\right)+\left(-111\right)+90\)
\(=258+\left[\left(-79\right)+\left(-111\right)\right]+90\)
\(=258+\left(-190\right)+90\)
\(=258+\left(-100\right)\)
\(=158\)
b.\(\left(617-304\right)-\left(617+254\right)\)
\(=617-304-617-254\)
\(=617+\left(-304\right)+\left(-617\right)+\left(-254\right)\)
\(=\left[617+\left(-617\right)\right]+\left[\left(-304\right)+\left(-254\right)\right]\)
\(=0+\left(-558\right)\)
\(=-558\)
c.\(\left(217-372\right)-\left(217-465\right)-\left(465+372\right)\)
\(=217-372-217+465-465-372\)
\(=217+\left(-372\right)+\left(-217\right)+465+\left(-465\right)+\left(-372\right)\)
\(=\left[217+\left(-217\right)\right]+\left[\left(-372\right)+\left(-372\right)\right]+\left[465+\left(-465\right)\right]\)
\(=0+\left(-744\right)+0\)
\(=-744\)
d.\(\left(x+y+z+t\right)-\left(x+y+z-t\right)-\left(y+z+t-x\right)-\left(z+t+x-y\right)-\left(t+x+y-z\right)\)
\(=x+y+z+t-x-y-z+t-y-z-t+x-z-t-x+y-t-x-y+z\)viết hoài mỏi tay nên khúc sau tự làm nhé ^_^
Bỏ ngoặc rồi tính
(a + 90) - (a + 45)
=a+90-a-45
=90-45
=45
(a + 90) - (a + 45)
= a+90 - a - 45
= ( a-a ) + ( 90 - 45 )
= 0 + 45
=45
-a+b-c-a-b-c
=(b-b)-a-a-c-c
=0-(a-a)-c-c
=0-0-c-c
=0-0-0
=0
\(\left(27+55\right)+\left(345-27-55\right)\)
\(=27+55+345-27-55\)
\(=\left(27-27\right)+\left(55-55\right)+345\)
\(=0+0+345\)
\(=345\)
\(38.65+38.50-38.15\)
\(=38.\left(65+50-15\right)\)
\(=38.100\)
\(=3800\)
\(\left(123-60\right)-\left(2017-60+123\right)\)
\(=123-60-2017+60-123\)
\(=\left(123-123\right)-\left(60-60\right)-2017\)
\(=0-0-2017\)
\(=-2017\)
Bỏ dấu ngoặc rồi tính:
(27 + 55 ) + ( 345 - 27 - 55 )
= 27 + 55 + 345 - 27 - 55
= (27-27) + (55-55) + 345
= 0 + 0 + 345
= 345
Tính nhanh:
38.65 + 38.50 - 38.15
= 38.(65+50-15)
= 38.100
= 3800
Bỏ ngoặc rồi tính:
( 123 - 60 ) - ( 2017 - 60 + 123 )
= 123 - 60 - 2017 + 60 - 123
= (123-123) + (60-60) - 2017
= 0 + 0 - 2017
= 0 - 2017
= -2017
- ( 73 ) + ( 44 - 94 + 27 ) + 94
= -73 + 44 - 94 + 27 + 94
=( -73 + 44 + 27 ) + ( -94 + 94 )
= -2 + 0 = -2
- 73 + ( 44 - 94 + 27 ) + 94
= - 73 + 44 - 94 + 27 + 94
= ( 94 - 94 ) + ( - 73 + 27 ) + 44
= 0 + ( - 46 ) + 44
= - 2
-(3251+415)-(2000+585-251)
= -3251-415-2000-585+251
=(-3251+251)+(415+585)+2000
=-3000 + 1000 + 2000
=0
k cho mk nhoa
a) ( - 385 + 210 ) + ( 285 - 217 )
= - 385 + 210 + 285 - 217
= ( - 385 + 285 ) + ( 210 - 217 )
= - 100 - 7= - 107Sai rùi