\(\dfrac{7}{19}x\dfrac{8}{23}+\dfrac{7}{19}x\dfrac{15}{23}+1\dfrac{7}{19}\)

= \(\dfrac{7}{19}x\left(\dfrac{8}{23}+\dfrac{15}{23}\right)+1+\dfrac{7}{19}\)

=\(\dfrac{7}{19}x1+1+\dfrac{7}{19}\)

= \(\dfrac{7}{19}+1+\dfrac{7}{19}=1\dfrac{14}{19}\) = \(\dfrac{33}{19}\)

\(\dfrac{75}{100}+\dfrac{18}{21}+\dfrac{49}{32}+\dfrac{1}{4}+\dfrac{3}{21}-\dfrac{17}{32}\)

=  \(\dfrac{3}{4}+\dfrac{6}{7}+\dfrac{49}{32}+\dfrac{1}{4}+\dfrac{1}{7}-\dfrac{17}{32}\)

= \(\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\left(\dfrac{6}{7}+\dfrac{1}{7}\right)+\left(\dfrac{49}{32}-\dfrac{17}{32}\right)\)

= 1 + 1 + 1 = 3

\(\dfrac{8}{9}x\dfrac{15}{16}x\dfrac{24}{25}x\dfrac{35}{36}x\dfrac{48}{49}x\dfrac{63}{64}\)

= \(\dfrac{3}{4}\) *Câu này bạn tự sử dụng gạch nhé!

`1,`

`a,`

`7/19 \times 8/23 + 7/19 \times 15/23 + 1 7/19`

`= 7/19 \times 8/23 + 7/19 \times 15/23 + 1 + 7/19`

`= 7/19 \times (8/23 + 15/23 + 1) + 1`

`= 7/19 \times 2 + 1`

`=14/19 + 1`

`= 33/19`

`b,`

`75/100 + 18/21 + 49/32 + 1/4 + 3/21 - 17/32`

`= 75/100 + (18/21 + 3/21) + (49/32 - 17/32) + 1/4`

`= 0,75 + 1 + 1 + 0,25`

`= (0,75 + 0,25) + 1 + 1`

`= 1+1+1=3`

`c,`

`8/9 \times 15/16 \times 24/25 \times 35/36 \times 48/49 \times 63/64`

`=` \(\dfrac{2\times3}{3\times3}\times\dfrac{3\times5}{4\times4}\times\dfrac{3\times4\times2}{5\times5}\times\dfrac{5\times7}{6\times6}\times\dfrac{6\times8}{7\times7}\times\dfrac{7\times9}{8\times8}\)

`= 3/4` (bạn sử dụng gạch, rút gọn các số là được nhé).

n: =345:(-345)=-1

n, (-15) x (-23) : (-345)

=   345  : (-345)

= -1

o, 36.55 - 185.11 + 121.5

 = 36.11.5 - 5.11.37 + 11.11.5

= 11.5.(36- 37 + 11)

= 11.5.10

= 550

\(27.77+24.27-27\)

\(=27.\left(77+24-1\right)\)

\(=27.100\)

\(=2700\)

\(174\div\left\{2\left[36+\left(4^2-23\right)\right]\right\}\)

\(=174\div\left\{2\left[36+\left(16-23\right)\right]\right\}\)

\(=174\div\left\{2\left[36+\left(-7\right)\right]\right\}\)

\(=174\div\left\{2.29\right\}\)

\(=174\div58\)

\(=3\)

\(3^2.4-\left[30-\left(5-2\right)^2\right]\)

\(=9.4-\left[30-3^2\right]\)

\(=36-\left[30-9\right]\)

\(=36-21\)

\(=15\)

a) 100 - (3 - 3⁵ - 3 . 3³)

= 100 - (3 - 243 - 3 . 27)

= 100 - (3 - 243 - 81)

= 100 - (-321)

= 421

b) 27 . 76 + 24 . 27 + 260

= 27 . (76 + 24) + 260

= 27 . 100 + 260

= 2700 + 260

= 2960

`a,`

`31/23-(7/32+8/23)`

`=31/23-7/32-8/23`

`=(31/23-8/23)-7/32`

`=1-7/32=25/32`

`b,`

`38/45-(8/45-17/51-3/11)`

`=38/45-8/45+17/51+3/11`

`= (38/45-8/45)+17/51+3/11`

`=2/3+17/51+3/11`

`=1+3/11=14/11`

`c,`

`(1/3+12/67+13/41)-(79/67-28/41)`

`= 1/3+12/67+13/41-79/67+28/41`

`= 1/3+(12/67-79/67)+(13/41+28/41)`

`= 1/3+(-1)+1=1/3+(-1+1)=1/3+0=1/3`

`d,`

`1/5+(-1/6)+1/7+(-1/8)+1/9+1/8+(-1/7)+1/6+(-1/5)`

`= (1/5+ -1/5)+(-1/6+1/6)+(1/7+ -1/7)+(-1/8 +1/8)+1/9`

`= 0+0+0+0+1/9=1/9 .`

\(a.415\times7-415\times5+415\times8\)

\(=415\times\left(7-5+8\right)=415\times10=4150\)

\(b.23\times87+12\times23+23\)

\(=23\times\left(87+12+1\right)=23\times100=2300\)

a. 415 x 7 - 415 x 5 + 4 15  x 8

= 415 x ( 7 - 5 + 8 )

= 415 x 10

= 41 50

b. 23 x 87 + 1 2 x 23 + 2 3

= 23x 87 + 12 x 23 + 23 x 1

= 23 x ( 87  + 12 + 1 )

= 23 x 100

= 2300

= 

a) 22+36=58     96−32=64     62−30=32

89−47=42     44+44=88     45−5=40

\(\frac{24.27-23}{24+47.23}=\frac{648-23}{24+1081}=\frac{625}{1105}=\frac{125}{221}\)

_Học_tốt_

=^.^=

\(\frac{24.27-23}{24+47.23}\\ =\frac{\left(23+1\right).27-23}{23+1+47.23}\\ =\frac{23.27+27-23}{23.\left(47+1\right)+1}\\ \)

\(\frac{24.27-23}{24+47.23}=\frac{648-23}{24+1081}=\frac{625}{1105}=\frac{125}{221}\)