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

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

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

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

a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7

= 15 / 17 x (4 / 7 + 3 / 7)

=15 / 17 x 1=15 / 17 

b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2 

=29 / 12  x2 - 5 / 12 x 2 

=(29 / 12 - 5 / 12)x2

=2x2=4

a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7

= 15 / 17 x (4 / 7 + 3 / 7)

=15 / 17 x 1=15 / 17 

b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2 

=29 / 12  x2 - 5 / 12 x 2 

=(29 / 12 - 5 / 12)x2

=2x2=4

chúc bạn học tốt !

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

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

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

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

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

\(a.=\left(\dfrac{4}{5}.\dfrac{5}{6}\right).\dfrac{2}{3}=\dfrac{4}{6}.\dfrac{2}{3}=\dfrac{4}{9}\)

\(b.\dfrac{4}{5}.\dfrac{3}{4}+\dfrac{5}{4}.\dfrac{3}{4}=\dfrac{3}{5}+\dfrac{15}{16}=\dfrac{123}{80}\)

\(c.\left(\dfrac{11}{23}+\dfrac{9}{23}\right)+\left(\dfrac{2}{23}+\dfrac{18}{23}\right)=\dfrac{20}{23}+\dfrac{20}{23}=\dfrac{40}{23}\)

\(d.\left(\dfrac{27}{12}-\dfrac{25}{36}\right)+\left(\dfrac{17}{6}-\dfrac{15}{6}\right)=\dfrac{14}{9}+\dfrac{1}{3}=\dfrac{17}{9}\)

dấu chấm là gì vậy

dấu chấm là dấu x trong cấp trên

bn chiệt tiêu ra nhé

a) \(60\times\left(\frac{7}{12}+\frac{4}{15}\right)=\frac{60\times7}{12}+\frac{60\times4}{15}\)

                                           \(=\frac{12\times5\times7}{12}+\frac{15\times4\times4}{15}\)

                                           \(=5\times7+4\times4\)

                                            \(=35+16\)

                                            \(=51\)

a: \(=\dfrac{21}{11}+\dfrac{12}{11}+\left(-\dfrac{9}{19}-\dfrac{3}{19}-\dfrac{6}{19}\right)=3-\dfrac{18}{19}=\dfrac{39}{19}\)

b: \(=\dfrac{2}{3}+\dfrac{4}{3}+\dfrac{3}{4}+\dfrac{7}{4}+\dfrac{4}{5}+\dfrac{16}{5}=2+4+\dfrac{5}{2}=6+\dfrac{5}{2}=\dfrac{17}{2}\)

a ( 1+2+3+4+....+99)*(13*15-12*25-15)
= ( 1+2+3+4+....+99)*[15*(13-1)-12*25)]
=( 1+2+3+4+....+99)*[15*12-12*25]
=( 1+2+3+4+....+99)*[12*(15-25)]
=( 1+2+3+4+....+99)*[12*(-10)]
=( 1+2+3+4+....+99)*(-120)
= -594000
b 3*5*36+15+42+30*11
=15*36+15*1+42+15*22
=15*(36+1+22)+42
=15*59+42
=885+42
=927
Tick cho mk nha
 

a. ( 1+2+3+4+....+99)*(13*15-12*25-15)

=( 1+2+3+4+....+99) . 0

=0

 b 3*5*36+15+42+30*11

=540 + 15 +42 + 330

=927

1111+2517536251673521735123517338276349-24546575643356435321=

15 x 6= 90

+ 48= 138 nha 

TL: 

8/15 x 5/6 = 40/90 = 4/9 

41/20 x 3/4 = 123/80 

(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43 

HT

\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)

\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)

\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)

/HT\

Nhập các bạn toàn bắt tớ làm à ngu gò mà làm