a. 1 x 9

= 9

b. 9 x 8 x 9

= (9 x 9) x 8

= 81 x 8

= 648

c. 10 x 8 x 10

= (10 x 10) x 8

= 100 x 8

= 800

1*9=9

9*8*9=648

10*8*10=800

t nha

1 x 9 = 9

9 x 8 x 9 = 648

10 x 8 x 10 = 800

k mình nha ♥

1 + 2 + 8 + 9 + 1 + 2 + 8 + 9 + 10 + 10

= (1 + 9) + (1 + 9) + (2 + 8) + (2 + 8) + 10 + 10

=    10    +     10   +     10   +    10    + 10 + 10

=      60

=1+9+2+8+1+9+2+8+10+10

=10+10+10+10+10+10

=10x6

=60

k mk nha mk k lại!

ket 

qua bnga 60

1/10+2/9+3/8+4/7+5/6+1/6+3/7+5/8+7/9+9/10

=(1/10+9/10)+(2/9+7/9)+(3/8+5/8)+(4/7+3/7)+(5/6+1/6)

=1+1+1+1+1

=5

1/10 + 2/9 + 3/8 + 4/7 + 5/6 + 1/6 + 3/7 + 5/8 + 7/9 + 9/10

= ( 1/10 + 9/10 ) + ( 2/9 + 7/9 ) + ( 3/8 + 5/8 ) + ( 4/7 + 3/7 ) + ( 5/6 + 1/6 )

= 10/10 + 9/9 +8/8 +7/7 +6/6

= 1 + 1 + 1 + 1 + 1

= 5 .

1/10 + 2/9 +3/8 + 4/7 + 5/6 + 1/6 + 3/7 + 5/8 + 7/9 + 9/10=5

    \(\dfrac{8}{3}\)x\(\dfrac{15}{3}+\dfrac{4}{3}\) x \(\dfrac{41}{9}+\dfrac{10}{9}\) x \(\dfrac{4}{3}\)

​\(=\dfrac{8}{3}\) x \(\dfrac{15}{3}+\dfrac{4}{3}\) x \(\left(\dfrac{41}{9}+\dfrac{10}{9}\right)\)​

\(=\dfrac{40}{3}+\dfrac{4}{3}\) x ​\(\dfrac{17}{3}\)

\(=\dfrac{188}{9}\)

1+2+3+4+5+6+7+8+9+10+11+12+13-1-2-3-4-5-6-7-8-9-10-11-12

=(1-1)+(2-2)+(3-3)+(4-4)+(5-5)+(6-6)+(7-7)+(8-8)+(9-9)+(10-10)+(11-11)+(12-12)+13

=  0  +  0  +  0  +  0  +   0  +  0  +  0  +  0  +  0  + 0  + 0   +  0  +  13

=                                 13

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 - 1 - 2 - 3 - 4 - 5 - 6 - 7- 8 - 9 - 10 

= (1+12) + (2+11) + (3+10) + ( 4+9) + (5+8) + (6+7) + 13 -  (1+11) - ( 2+10) - ( 3+9) - (4+8) - (5+7) + 6 + 12

= 13 * 7 - 12 * 6 + 6

= 13

Ai k mk mk k lại

= 13 nhé hihi nha

Bằng 7200 nha bạn k cho mik i

7x8x9x10 + 2x3x4x5x2x9 = 7x8x9x10 + 3x8x10x9

                                          = 8x9x10 x (7+3)

                                          = 720 x 10

                                          = 7200

Chúc bạn hok tốt nha!@