Câu 1:
a)17-{-x-[-x-(-x)]}=-16
⇒17+x-x+x=-16
⇒17+x=-16
⇒x=-33
b)x+{(x+3)-[(x+3)-(-x-2)]}=x
⇒x+x+3-x-3+x+2=x
⇒2x+2=x
⇒2x-x=-2
⇒x=-2
Câu 2:
a)x+45-[90+(-20)+5-(-45)]
=x+45-90+20-5-45
=x+(45-45)+(-90+20-5)
=x+0+(-75)
=x-75
b)x+(294+13)+(94-13)
=x+294+13+94-13
=x+(294+94)+(13-13)
=x+388+0
=x+388
Câu 3:
a)-b-(b-a+c)
=-b-b+a-c
=-2b+a-c
b)-(a-b+c)-(c-a)
=-a+b-c-c+a
=b-2c
c)b-(b+a-c)
=b-b-a+c
=-a+c
d)a-(-b+a-c)
=a+b-a+c
=b+c
Câu 4:
a, N=-{-(a+b)-[(a-b)-(a+b)]}
⇒N=a+b+a-b+a+b
⇒N=3a+b
b, Tại a=-5; b=-3, ta có:
N=3.(-5)+(-3)
⇒N=-15-3
⇒N=-18