thực hiện phép tính a.(-2009)-(234-2009) b.(134-167+45)-(134+45) c.321+{-15+[30+(-321)]} d.1000-(137+572)+(263-291) giúp em em vote 5 sao ạ

a. (-2009)-(234-2009)
=(-2009+2009)-234
=0-234=-234
b. (134-167+45)-(134+45)
=134-167+45-134-45
= (134-134)+(45-45 )-167
=0-0-167
=-167
c. 321+{-15+[30+(-321)]}

= 321+(-15)+30+(-321)
= [321+(-321)]+[(-15)+30]
= 0+15 = 15
d. 1000-(137+572)+(263-291)
= 1000-137-572+263-291
=1000+263-(137+572+291)
=1000+263-1000
=263

a)(-2009 ) - ( 234 - 2009 )

= (-2009 ) - 234 + 2009 = ( -2009 + 2009 ) -234 = 0- 234 = -234
b) (134-167+45)-(134+45)
= 134 - 167 + 45 - 134 - 45

= ( 134 - 134 ) + ( 45 - 45 ) - 167 = 0 - 0 - 167 = -167
c) 321+{-15+[30+(-321)]} 
= 321+(-15)+30+(-321)

= [321+(-321)]+[(-15)+30]

= 0+15

= 15
d)1000-(137+572)+(263-291)
= 1000-137-572+263-291
=1000+263-(137+572+291)
=1000+263-1000=263