\(\dfrac{2}{3}\times\dfrac{4}{9}+\dfrac{2}{3}\times\dfrac{5}{9}\\ =\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\\ =\dfrac{2}{3}\times\dfrac{9}{9}\\ =\dfrac{2}{3}\times1\\ =\dfrac{2}{3}.\)

`2/3 xx 4/9 + 2/3 xx 5/9 `

`= 2/3 xx (4/9 + 5/9)`

`= 2/3 xx 1`

`= 2/3`

DS:11/5 DS: 10

7/11:3/5+4/11:3/5

=(7/11+4/11):3/5

=1:3/5

=1x5/3

=\(\frac{5}{3}\)

(6,24+1,26);0,75

=7,5:0,75

=10

\(\frac{7}{11}:\frac{3}{5}+\frac{4}{11}:\frac{3}{5}=\frac{3}{5}:\left(\frac{7}{11}+\frac{4}{11}\right)=\frac{3}{5}:1=\frac{5}{3}\)

\(\left(6,24+1,26\right):0,75=7,5:0,75=10\)

\(E=1-2+3-4+5-6+7-8+...+99-100+101\)

\(E=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+\left(7-8\right)+...+\left(99-100\right)+101\)(Có 50 cặp)

\(E=\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)+101\)(Có 50 số -1)

\(E=\left(-1\right).50+101\)

\(E=\left(-50\right)+101\)

\(E=51\)

E=45 nhé

nhầm 51 nhé

=(2×5)×(9×7)×(4×25)

=10×63×100

=63000

*Dấu . là dấu nhân nhá
a)2.9.5.7.4.25
=(2.5).(4.25).(9.7)
=10.100.63
=1000.63
=63000
b)6.14.5.4.2.25
=(2.5).(4.25).(14.6)
=10.100.84
=1000.84
=84000

=(2×5)×(9×7)×(4×25)

=10×63×100

=63000

1*2*3*4*5*6*7*8/2*3*4*5*6*7*8*9=1/9

ê = 1/9

1x2x3x4x5x6x7x8/1x2x3x4x5x6x7x8x9=1/9