a) \(\dfrac{x^2}{x+1}+\dfrac{2x}{x^2-1}+\dfrac{1}{1+x+1}\) \(=\dfrac{x^2.\left(x-1\right)\left(x+2\right)}{\left(x+1\right).\left(x-1\right)\left(x+2\right)}+\dfrac{2x.\left(x+2\right)}{\left(x-1\right).\left(x+1\right).\left(x+2\right)}+\dfrac{\left(x-1\right).\left(x+1\right)}{\left(x-1\right)\left(x+1\right).\left(x+2\right)}\)

\(=\dfrac{x^2.\left(x-1\right).\left(x+2\right)+2x.\left(x+2\right)+\left(x-1\right)\left(x+1\right)}{\left(x+1\right).\left(x-1\right).\left(x+2\right)}\)

\(=\dfrac{x^4+x^3-2x^2+2x^2+4x+x^2-1}{\left(x-1\right)\left(x+1\right).\left(x+2\right)}\)

\(=\dfrac{x^4+x^3+x^2+4x-1}{\left(x^2-1\right).\left(x+2\right)}\)

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

a) b 3 + 3 b 2 + 2 b 3 + 1 .          b) 0.

`a, a/(a-3) - 3/(a+3) = (a(a+3) - 3(a-3))/(a^2-9)`

`= (a^2+9)/(a^2-9)`

`b, 1/(2x) + 2/x^2 = x/(2x^2) + 4/(2x^2) = (x+4)/(2x^2)`

`c, 4/(x^2-1) - 2/(x^2+x) = (4x)/(x(x-1)(x+1)) - (2(x-1))/(x(x+1)(x-1))`

`= (2x+2)/(x(x-1)(x+1)`

`= 2/(x(x-1))`

a) \(\dfrac{a-1}{a+1}+\dfrac{3-a}{a+1}\)

\(=\dfrac{a-1+3-a}{a+1}\)

\(=\dfrac{2}{a+1}\)

b) \(\dfrac{b}{a-b}+\dfrac{a}{b-a}\)

\(=\dfrac{b}{a-b}+\dfrac{-a}{a-b}\)

\(=\dfrac{b-a}{a-b}\)

\(=-1\)

c) \(\dfrac{\left(a+b\right)^2}{ab}-\dfrac{\left(a-b\right)^2}{ab}\)

\(=\dfrac{\left[\left(a+b\right)-\left(a-b\right)\right]\left[\left(a+b\right)+\left(a-b\right)\right]}{ab}\)

\(=\dfrac{4ab}{ab}\)

\(=4\)

`a, (a-1)/(a+1) + (3-a)/(a+1)`

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

`=2/(a+1)`

`b, b/(a-b) + a/(b-a)`

`=  b/(a-b) - a/(a-b)`

`= (b-a)/(a-b)`

`c, (a+b)^2/(ab) -(a-b)^2/(ab)`

`=(a^2+2ab+b^2-a^2+2ab-b^2)/(ab)`

`= (4ab)/(ab)`

a: \(=\dfrac{3b+4a}{6ab}\)

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

c: \(=\dfrac{xz+yz-xy-xz}{xyz}=\dfrac{yz-xy}{xyz}=\dfrac{z-x}{xz}\)

d: \(=\dfrac{2x+6-12}{\left(x-3\right)\left(x+3\right)}=\dfrac{2x-6}{\left(x-3\right)\left(x+3\right)}=\dfrac{2}{x+3}\)

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

Hãy cộng phân số sau:

a) 3/5 + 4/5=7/5

b) 9/3 + 1/3=10/3

c) 10/7 + 5/7=15/7

d) 8/4 + 2/4=10/4

e) 7/6 + 3/6=10/6

a)7/5

b)10/3

c)15/7

d)10/4=5/2

e)10/6=5/3 nhé =)

a: 3/5+4/5=7/5

b: =10/3

c: =15/7

d: =10/4=5/2

e: =10/6=5/3

\(a,\dfrac{x}{x+3}+\dfrac{2-x}{x+3}\\ =\dfrac{x+2-x}{x+3}\\ =\dfrac{2}{x+3}\\b,\dfrac{x^2y}{x-y}-\dfrac{xy^2}{x-y}\\ =\dfrac{x^2y-xy^2}{x-y}\\ =\dfrac{xy\left(x-y\right)}{x-y}\\ =xy\\ c,\dfrac{2x}{2x-y}+\dfrac{y}{y-2x}\\=\dfrac{2x}{2x-y}-\dfrac{y}{2x-y}\\ =\dfrac{2x-y}{2x-y}\\ =1 \)

`a, x/(x+3) + (2-x)/(x+3) = (x+2-x)/(x+3) = 2/(x+3)`

`b, (x^2y)/(x-y) - (xy^2)/(x-y) = (x^2y-xy^2)/(x-y) = (xy(x-y))/(x-y)= xy`

`c, (2x)/(2x-y) - (y)/(2x-y)`

`= (2x-y)/(2x-y) = 1`

cíuuu

a: =căn 3+căn 5-căn 3=căn5
b: \(=\sqrt{x-2-2\sqrt{x-2}+1}=\sqrt{\left(\sqrt{x-2}-1\right)^2}\)

\(=\left|\sqrt{x-2}-1\right|\)

D

C 

\(\dfrac{5}{6}\)

Câu 1: 

a: IV

b: S hóa trị 6

\(1.a.IV\\ b.VI\)

\(2.a.P_2O_5\\ b.NH_3\)