mk ko bt sorry 

ai vậy thì k mk nha 

\(=\frac{28}{45}\)

a)1/2

b)49/1300

12/15 = 4/5                                                 15/10 = 3/2

14/21 = 2/3                                                 70/20 = 7/2

18/12 = 3/2                                                  55/66 = 5/6

( 4/5 - 2/3 - 3/2 ) : ( 3/2 - 7/2 - 5/6 ) = -41/30 : -17/6

                                                   = 41/85

\(1+6-2+9-55+77.88:44:2.11:121=-41+7=-34\)

1+6-2+9-55+77 . 88 : 44 : 2 . 11 : 121

= 1+6-2+9-55+7

= -34

Bài 2: 

a: \(A=\dfrac{11\cdot10\left(1+5\cdot5+7\cdot7\right)}{11\cdot12\left(1+5\cdot5+7\cdot7\right)}=\dfrac{10}{12}=\dfrac{5}{6}\)

\(B=\dfrac{1}{8}\cdot\dfrac{125}{5}\cdot\dfrac{81}{81}\cdot\dfrac{64}{8}=25\)

396,99

tick nhé 

mình nhanh nhất

ai tick mik mik tick lại cho

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

11+22+33+44+55+66+77+88+99=495 nhé.

11 + 22 + 33 + 44 + 55 + 66 + 77 +88 + 99

= ( 11 + 99 ) + ( 88 + 22 ) + ( 33 + 77 ) + ( 44 + 66 ) + 55

= 100 + 100 + 100 + 100 + 55

= 100 x 4 + 55

= 400 + 55

= 455