Bài 1

\(a,18,5:4,6+14,8:4,6+12,7:4,6\)

\(=18,5\times\dfrac{1}{4,6}+14,8\times\dfrac{1}{4,6}+12,7\times\dfrac{1}{4,6}\)

\(=\dfrac{1}{4,6}\times\left(18,5+14,8+12,7\right)\)

\(=\dfrac{1}{4,6}\times46\)

\(=10\)

\(b,0,75\times1,3+0,25\times1,3\)

\(=1,3\times\left(0,75+0,25\right)\)

\(=1,3\times1\)

\(=1,3\)

\(c,\left(7,91+5,09-6,05-6,95\right):31,792\)

\(=\left(13-13\right):31,792\)

\(=0:31,792\)

\(=0\)

\(d,\dfrac{5,7.16,2+16,2.3,7-6,2.4,8-6,2.4,6}{13,4+12,3+11,2-10,4-11,5-12,6-0,4}\)

\(=\dfrac{16,2\left(5,7+3,7\right)-6,2\left(4,8+4,6\right)}{2}\)

\(=\dfrac{16,2.9,4-6,2.9,4}{2}\)

\(=\dfrac{9,4\left(16,2-6,2\right)}{2}\)

\(=\dfrac{94}{2}=47\)

\(\left(2.\dfrac{2}{15}.\dfrac{9}{17}.\dfrac{3}{32}\right):\left(-\dfrac{3}{7}\right)\)

\(=\dfrac{9}{680}:\left(-\dfrac{3}{7}\right)\)

\(=-\dfrac{21}{680}\)

Gọi số sản phẩm của 2 đội là a ( 200<a<400)

Ta có

\(20=2^2\times5\)

\(45=3^2\times5\)

\(\Rightarrow a\in BC\left(20,45\right)=\left\{0,180,360,540,...\right\}\)

Vì \(200< a< 400\)

\(\Rightarrow a=360\) ( hai đội công nhân cùng làm 1 số SP như nhau)

Vậy đội một làm 360 sp đội 2 làm 360sp

-15+8+12+(-5)

= (-15-5)+(8+12)

=-20+20

=0

$A=8abc+4\left(ab+bc+ca\right)+2\left(a+b+c\right)+1$

A = 8abc + 4ab + 4bc + 4ca + 2a + 2b + 2c + 1

$A=\left(8abc+4ab\right)+\left(4bc+2b\right)+\left(4ca+2a\right)+\left(2c+1\right)$

$A=4ab\left(2c+1\right)+2b\left(2c+1\right)+2a\left(2c+1\right)+\left(2c+1\right)$

$A=\left(2c+1\right)\left(4ab+2a+2b+1\right)$

$A=\left(2c+1\right)\left[2a\left(2b+1\right)+\left(2b+1\right)\right]$

$A=\left(2a+1\right)\left(2b+1\right)\left(2c+1\right)$

bỏ cái cuối đi e nhé(246=...) máy bị nhảy nên có 

Ta cos

\(360=2^3\times3^5\times5\)

\(246=2\times3\times41\)

\(220=2^2\times5\times11\)

=>\(BCNN\left(360,246,220\right)=2^3=8\)

\(246=2\times3\times41\)

\(\dfrac{3}{4}+\dfrac{3}{28}+\dfrac{3}{70}+\dfrac{3}{130}+\dfrac{3}{208}+\dfrac{3}{304}\)

\(=\dfrac{3}{1\times4}+\dfrac{3}{4\times7}+\dfrac{3}{7\times10}+\dfrac{3}{10\times13}+\dfrac{3}{13\times16}+\dfrac{3}{16\times19}\)

\(=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{19}\)

\(=1-\dfrac{1}{19}\)

=\(\dfrac{18}{19}\)

Gọi 3 số chẵn liên tiếp lần lượt là: x, x+2,x+4

Theo đề bài ta có

(x+2)(x+4)-x(x+2)=192

(x+2)(x+4-x)=192

(x+2)4=192

x+2=192:4

x+2=48

=> x=46

=> x+2=48

=> x+4=50

Vậy 3 số chẵn liên tiếp lần lượt là 46,48,50

8x -16(x-5)=0

8x-16x+80=0

8x - 16x=0-80

x.(8-16)=-80

x.(-8)=-80

x=-80:(-8)

x=10

Vậy x=10