Bài 1: 

b: \(=\dfrac{x+3-4-x}{x-2}=\dfrac{-1}{x-2}\)

Bài 2: 

a: \(=\dfrac{x+1}{2\left(x+3\right)}+\dfrac{2x+3}{x\left(x+3\right)}\)

\(=\dfrac{x^2+x+4x+6}{2x\left(x+3\right)}=\dfrac{x^2+5x+6}{2x\left(x+3\right)}=\dfrac{x+2}{2x}\)

d: \(=\dfrac{3}{2x^2y}+\dfrac{5}{xy^2}+\dfrac{x}{y^3}\)

\(=\dfrac{3y^2+10xy+2x^3}{2x^2y^3}\)

e: \(=\dfrac{x^2+2xy+x^2-2xy-4xy}{\left(x+2y\right)\left(x-2y\right)}=\dfrac{2x^2-4xy}{\left(x+2y\right)\cdot\left(x-2y\right)}=\dfrac{2x}{x+2y}\)

7/3/8 - 4/5/8 = 59/8 - 37/8 = 12

2/1/4 +5/1/4 = 9/4 + 21/4 = 15/2

3/1/4 x 2/3/5 = 13/4 x 13/5 =11/20

\(7\frac{3}{8}-4\frac{5}{8}=\frac{59}{8}-\frac{37}{8}=\frac{22}{8}\)\(=\)\(2,75\)

\(2\frac{1}{4}+5\frac{1}{4}=\frac{9}{4}+\frac{21}{4}=\frac{30}{4}=7,5\)

\(3\frac{1}{4}\times2\frac{3}{5}=\frac{13}{4}\times\frac{13}{5}=\frac{169}{20}=8,45\)

#Minyun

a)

160 : (4 × 8) = 160 : 32 = 5

160 : 4 : 8 = 40 : 8 = 5

Vậy 160 : (4 × 8) = 160 : 4 : 8.

96 : (3 × 8) = 96 : 24 = 4

96 : 3 : 8 = 32 : 8 = 4

Vậy 96 : (3 × 8) = 96 : 3 : 8.

105 : (5 × 7) = 105 : 35 = 3

105 : 5 : 7 = 21 : 7 = 3

Vậy 105 : (5 × 7) = 105 : 5 : 7.

Nhận xét: a : (b × c) = a : b : c

b)

270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5

420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20

144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9

Ta có: 

\(=\dfrac{x^2+2x-3x+6}{\left(x-2\right)\left(x+2\right)}\cdot\dfrac{2\left(x-2\right)\left(x+2\right)}{x-3}\)

\(=\dfrac{2\left(x^2-x+6\right)}{x-3}\)

Ta có : 1x2x3x...x9-1x2x3x...x8-1x2x3x...x8^2

=1x2x3x...x8x(9-1-8)

=1x2x3x...x8x0

=0

Nhớ  k cho mik nha !!!

4kg x 9 – 28kg = 36kg – 28kg = 8kg

3 x 8 : 4 = 24 : 4 = 6

5 × 8 + 8 = 40 + 8 = 48

28 - 2 × 4 = 28 – 8 = 20

C