a) 18/15 + 7/15 + 12/15 =18/15 + 12/15 + 7/15        

                                    = 30/15 + 7/15

                                     =       37/15

b) 9/7 + 8/7 +11/7 = 9/7 + 11/7 + 8/7 

                         =  20/7  + 8/7 =  28/7 nha . tk mk nhé b

a, 18/15+7/15+12/15= 37/15

b, 9/7+8/7+11/7=28/7=4

a ) \(\frac{18}{15}\)+ \(\frac{7}{15}\)+ \(\frac{12}{15}\)= \(\frac{37}{15}\)

b )\(\frac{9}{7}\)+ \(\frac{8}{7}\)+ \(\frac{11}{7}\)= 4

a,18/15+7/15+12/15=18+7+12/15

                             =37/15

b,9/7+8/7+11/7=9+8+11/7

                      =28/7=1/4

+8/15 + 7/15 +12/15 = (18+7+12)/7 = [(18+12)+7]/15= (30+7)/15=37/15=7/3

9/7 + 8/7 + 11/7 = (9+8+11)/7= [(9+11)+8]/7=(20+8)/7= 28/7 =4

a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)

b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)

a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)

\(=\left(\frac{18}{15}+\frac{12}{5}\right)+\frac{7}{15}\)

\(=6+\frac{7}{15}\)

\(=\frac{97}{15}\)

b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)

\(=\frac{17}{7}+\frac{11}{7}\)

\(=\frac{28}{7}=4\)

TL

a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)\(=\frac{97}{15}\)

b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)\(=4\)

nha bn

HT

A = (2 + 2²) + (2³ + 2⁴ ) +…(2¹⁹⁹ + 2²⁰⁰)

A = 6 + 2² (2 + 2² ) +… + 2¹⁹⁸ (2 + 2²)

A = 6 + 2² (6 ) +… + 2¹⁹⁸ (6)

A = 6(1 + 2² +… + 2¹⁹⁸)

Vậy A chia hết cho 6

a) \(\left(\frac{2}{7}+\frac{3}{8}+\frac{12}{7}+\frac{5}{8}\right).\frac{19}{36}\)

\(=\left\{\left(\frac{2}{7}+\frac{12}{7}\right)+\left(\frac{3}{8}+\frac{5}{8}\right)\right\}.\frac{19}{36}\)

\(=\left(\frac{14}{7}+\frac{8}{8}\right).\frac{19}{36}\)

\(=\left(2+1\right).\frac{19}{36}\)

\(3.\frac{19}{36}=\frac{19}{12}\)

Please

a) \(...=-\dfrac{12}{46}-\dfrac{15}{21}+\dfrac{3}{7}-\dfrac{7}{23}\)

\(=-\dfrac{12}{46}-\dfrac{7}{23}-\dfrac{15}{21}+\dfrac{3}{7}\)

\(=-\dfrac{6}{23}-\dfrac{7}{23}-\dfrac{5}{7}+\dfrac{3}{7}\)

\(=-\dfrac{13}{23}-\dfrac{2}{7}\)

\(=-\dfrac{13.7}{23.7}-\dfrac{2.23}{23.7}\)

\(=-\dfrac{91}{161}-\dfrac{46}{161}=-\dfrac{137}{161}\)

b) \(...=-21+\dfrac{7}{9}-\dfrac{3}{17}+\dfrac{25}{9}\)

\(=-21-\dfrac{3}{17}+\dfrac{7}{9}+\dfrac{25}{9}\)

\(=-21-\dfrac{3}{17}+\dfrac{32}{9}\)

\(=-\dfrac{3213}{153}-\dfrac{27}{153}+\dfrac{544}{153}=-\dfrac{2696}{153}\)

\(\frac{11}{15}\cdot\frac{6}{7}+\frac{11}{15}\cdot\frac{8}{7}\) 

\(=\frac{11}{15}\cdot\left(\frac{6}{7}+\frac{8}{7}\right)\) 

\(=\frac{11}{15}\cdot2=\frac{22}{15}\)

Chú ý dấu "  \(\cdot\) " là dấu nhân

      11/15 x 6/7 + 11/15 x 8/7 

=    11/15 x (6/7 + 8/7)

=     11/15 x 2

=      22/15.

Mik ko chắc lắm nhé !

11/15 × 6/7 + 11/15 × 8/7

= 11/15x (6/7+8/7)

= 11/15x2

= 22/15

~Hok tốt~

A = ( 2/7 + 5/7 ) + 4/9

A =      1 + 4/9

A = 13/9

B = ( 17/11 + 5/11 ) + 7/15

B =        2 + 7/15

B = 37/15

Chúc bạn học tốt~^^

A = 2/7 + 4/9 + 5/7 

A = ( 2/7 + 5/7 ) + 4/9 

A = 1 + 4/9 

A  = 13/9                             

Phần B làm tương tự bằng cách bỏ ngoặc nhé !

A = \(\left(\frac{2}{7}+\frac{4}{9}\right)+\frac{5}{7}\)

A = \(\frac{2}{7}+\frac{5}{7}+\frac{4}{9}\)

A = 1 + \(\frac{4}{9}\)

A = \(\frac{13}{9}\)

B = \(\frac{17}{11}+\left(\frac{5}{11}+\frac{7}{15}\right)\)

B = \(\frac{17}{11}+\frac{5}{11}+\frac{7}{15}\)

B = 2 + \(\frac{7}{15}\)

B = \(\frac{37}{15}\)

Nếu mình đúng các bạn k mình nhé