ai lm tr mình cho tích

Ta có: \(A=1-2+3-4+5-6+7-8+9\)

\(=(1+9)-(2+8)+(3+7)-(4+6)+5\)

\(=10-10+10-10+5\)

\(=5\)

Vậy  \(A=5\) 

B = 12 - 14 + 16 - 18 + ... + 2008 - 2010

B = -2 + (-2)+ (-2)+ (-2) + ...+ (-2)

B = -2 . 100

B = -200

Bạn muốn kết bạn chứ

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

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

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

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

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

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

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

= 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).

 1*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*0*20*21*22*23*24*25*26*27*28*29*30*31*32=0

=0 vì tích có thừa số 0 

0 vì số nào nhân 0 cũng bằng0

\(a,\frac{7}{15}\cdot\frac{4}{5}+\frac{7}{15}\cdot\frac{1}{5}-\frac{7}{15}\)

\(=\frac{7}{15}\left(\frac{4}{5}+\frac{1}{5}-1\right)\)

\(=\frac{7}{15}\cdot0\)

\(=0\)

\(b,\frac{9}{25}\cdot\frac{7}{18}+\frac{9}{26}\cdot\frac{1}{3}+\frac{9}{25}\cdot\frac{1}{9}\)

\(=\frac{9}{25}\left(\frac{7}{18}+\frac{1}{3}+\frac{1}{9}\right)\)

\(=\frac{9}{25}\cdot\frac{5}{6}\)

\(=\frac{3}{10}\)

1)` 2/9 + -3/4 + 5/30= (40+(-135) + 30 )/180 = -65/180 = -13/36`

2) `-7/12 - 11/18=(-21)/36 - 22/36 = -43/36 `

3) `7/8 - (-5)/16=14/16- (-5)/16 = 19/16 `

4) `3/8 - (-9)/10 - 5/16= (30- (-72) -25)/80=77/80`

1)\(\dfrac{2}{9}+\dfrac{-3}{4}+\dfrac{5}{30}\)

\(=\dfrac{2.20}{9.20}+\dfrac{-3.45}{4.45}+\dfrac{5.6}{30.6}\)

\(=\dfrac{40}{180}+\dfrac{-135}{180}+\dfrac{30}{180}\)

\(=\dfrac{40+\left(-135\right)+30}{180}\)

\(=\dfrac{-65}{180}\)

\(=\dfrac{-13}{36}\)

2)\(\dfrac{-7}{12}-\dfrac{11}{18}\)

\(=\dfrac{-7.3}{12.3}-\dfrac{11.2}{18.2}\)

\(=\dfrac{-21}{36}-\dfrac{22}{36}\)

\(=\dfrac{-21-22}{36}\)

\(=\dfrac{-43}{36}\)

3)\(\dfrac{7}{8}-\dfrac{-5}{16}\)

\(=\dfrac{7.2}{8.2}-\dfrac{-5}{16}\)

\(=\dfrac{14}{16}-\dfrac{-5}{16}\)

\(=\dfrac{14-\left(-5\right)}{16}\)

\(=\dfrac{19}{16}\)

4)\(\dfrac{3}{8}-\dfrac{-9}{10}-\dfrac{5}{16}\)

\(=\dfrac{3.10}{8.10}-\dfrac{-9.8}{10.8}-\dfrac{5.5}{16.5}\)

\(=\dfrac{30}{80}-\dfrac{-72}{80}-\dfrac{25}{80}\)

\(=\dfrac{30-\left(-72\right)-25}{80}\)

\(=\dfrac{77}{80}\)

1+2+3+4+5+6+7+8+9+10=55

11+12+13+14+15+16+17+18+19+20=155

1+2+3+4+5+6+7+8+9+10+11+12+13+14 +15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30-50-53=362

1+2+3+4+5+6+7+8+9+10=55

11+12+13+14+15+16+17+18+19+20=155

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30-50-53=362

a, -5/11.7/15.(11/-5)(-30)

=(-5/11.11/-5).(7/15.-30)

=1.7.(-30)/15

=1.7.(-2).15/15

=1.7.(-2)

=-14

b,(11/12):(33/36).3/5

=11/12:(11.3/12.3).3/5

=11/12:11/12.3/5

=1.3/5

=3/5

c,(-5/-9).3/11+(-13/18).3/11

=5/9.3/11+ -13/18.3/11

=3/11.(5/9+ -13/18)

=3/11.(10/18+ -13/18)

=3/11.-3/18

= -9/198

= -1/22

Bài 2:

a,-7/15.5/8.15/7.(-16)

=(-7/15.15/7)(5/8. -16)

= -1.-10

= 10

b,(-1/-2).16/5+(-1/-2)(-11/5)

= 1/2.16/5+1/2. (-11/5)

=1/2.(16/5+ -11/5)

=1/2.5/5

=1/2.1

=1/2

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