C

c

Bài 4:

a: \(\overline{275x}\) ⋮5

=>x∈{0;5}

\(\overline{275x}\) ⋮25

=>\(\overline{5x}\) ⋮25

=>x=0

b: \(\overline{9xy4}\) ⋮2

=>(x;y)∈{(0;0);(0;1);...:(9;9)}

\(\overline{9xy4}\) ⋮4

=>\(\overline{y4}\) ⋮4

=>y∈{0;2;4;6;8}

=>(x;y)∈{(1;0);(1;2);(1;4);(1;6);(1;8);(2;0);(2;2);...;(9;0);(9;2);(9;4);(9;6);(9;8)}

\(\overline{9xy4}\) ⋮8

=>\(\overline{xy4}\) ⋮8

=>(x;y)∈{(1;0);(1;4);(1;8);(2;2);(2;6);(3;0);(3;4);(3;8);(4;2);(4;6);(5;0);(5;4);(5;8);(6;2);(6;6);(7;0);(7;4);(7;8);(8;2);(8;6);(9;0);(9;4);(9;8)}

Bài 2:

a chia 72 dư 18

=>a=72k+18

a=72k+18=2(36k+9)

=>a⋮2

a=72k+18=3(24k+6)

=>a⋮3

a=72k+18=72k+16+2=4(18k+4)+2

=>a không chia hết cho 4

a=72k+18=6(12k+3)⋮6

a=72k+18=72k+16+2=8(9k+2)+2

=>a không chia hết cho 8

a=72k+18

=9(8k+2)

=>a⋮9

a) \(A=\left\{x\in N|0\le x\le4\right\}\)

b) \(B=\left\{x\in N|x=4k;0\le k\le4;k\in N\right\}\)

c) \(C=\left\{x\in Z|x=\left(-3\right)^k;1\le k\le4;k\in N\right\}\)

d) \(D=\left\{x\in N|x=k^2;k=3a;1\le a\le4;a\in N\right\}\)

E vs F chịu à :)?

a)   8 . 4^5  - 3 . 9 . 12 + 28 : 4 . 2^0 = 7875

b)   210 + 86 . 2^3  : 2 - 19 . 23 = 117

c)   144 .12 + 83 . 11 - 17 . 3 = 2590

d)   54 . 23 + 11^2 - 152 = 1211

a) 8 . 4⁵ - 3 . 9 . 12 + 28 : 4 . 2⁰ = 7875

b) 210 + 86 . 2³ : 2 - 19 . 23 = 117

c) 144 . 12 + 83 . 11 - 17 . 3 = 2590

d) 54 . 23 + 11² - 152 = 1211

Câu 1: D

Câu 2: C

a)

\(=1001:11=91\)

b)

\(=196+25+4=200+25=225\)

c)

\(=29.31+144:144=899+1=900\)

d)

\(=111+225:225=111+1=112\)

a)=91

b)225

c)900

d)112