Câu 1:
a, 18-7+3
=11+3
=14
b, 15-(-23)+(-25)-23
=15+23-25-23
=(15-25)+(23-23)
=-10+0
=-10
c, 117-17.(3-4)
=117-17.(-1)
=117+17
=134
d, (-3-7).(3-7)
=-11.(-4)
=44
Bài 2:
a, 318-(-15+118)
=318+15-118
=(318-118)+15
=200+15
=215
b, (-2)^4 .17+(-16).7
=16.17-16.7
=17.(17-7)
=17.10
=170
c, 62.(22-40)-22.(62-40)
=62.22-62.40-22.62+22.40
=22.(62-62)+40.(-62+22)
=22.0+40.(-40)
=0+(-1600)
=-1600
Câu 3:
a, x-15=-21
⇒x=-21+15
⇒x=-6
b, 3.x+30=(-3)²
⇒3.x+30=9
⇒3.x=9-30
⇒3.x=-21
⇒x=-21:3
⇒x=-7
c, 2.|x+3|=18
⇒|x+3|=18:2
⇒|x+3|=9
⇒\(\left[ \begin{array}{l}x+3=9\\x+3=-9\end{array} \right.\) =>\(\left[ \begin{array}{l}x=6\\x=-12\end{array} \right.\)
Vậy x=6 hoặc x=-12
d, 12-(30-x)=-23
⇒30-x=12-(-23)
⇒30-x=35
⇒x=30-35
⇒x=-5
Câu 4:
a, Ta có: -6<x≤7
⇒x∈{-6;-4;-3;...;7}
b, Ta có: 7-2n$\vdots$n-2
⇒-2(n-2)+3$\vdots$n-2
⇒n-2∈Ư(3)={±1;±3}
n-2=1⇒n=3
n-2=-1⇒n=1
n-2=3⇒n=5
n-2=-3⇒n=-1
Vậy n∈{3;1;5;-1}
