1)
$1\in A$
$y\not\in A$
$y\in B$
$A\in B$
2)
$4^2-9[34-5^5:5^3]=16-9[34-5^2]=16-9[34-25]=16-9.9=16-81=-65$
3)
a, $7x-8=713$
$\to7x=713+8$
$\to7x=721$
$\to x=103$
Vậy $x=103$
b, $2248:[119-(x-6)]=24$
$\to119-x+6=\dfrac{281}{3}$
$\to125-x=\dfrac{281}{3}$
$\to x=\dfrac{94}{3}$
Vậy $x=\dfrac{94}{3}$
c, $2016-100(x+11)=2^7:2^3$
$\to2016-100(x+11)=2^4$
$\to2016-100(x+11)=16$
$\to100(x+11)=2000$
$\to x+11=20$
$\to x=9$
Vậy $x=9$.
4)
a, $-20≤x≤20$
`\to x\in{-20;-19;....19;20}`
Tổng các số nguyên $x$ là: $(-20)+(-19)+...+19+20=0$
b, $0≤x≤30$
`\to x\in{0;1;2;...;29;30}`
Tổng các số nguyên $x$ là:
$0+1+2+...+28+29+30$
$=1+2+...+28+29+30$
$=(30+1)[(30-1):1+1]:2=465$
7)
a, $x-36:18=12-15$
$→x-2=-3$
$→x=-3+2$
$→x=-1$
Vậy $x=-1$.
b, $16.4^x=4^8$
$→16.4^x=65536$
$→4^x=4096$
$→4^x=4^6$
$→x=6$
Vậy $x=6$.
c, $|x-2|+1=5$
$→|x-2|=4$
$→x-2=4$ hoặc $x-2=-4$
$→x=6$ hoặc $x=-2$
Vậy `x\in{-2;6}`.