Приготовляюсь к контрольной помогите пожалуйста номер 3

2.

a)5/3x+2/7x=(35+6)/21x=41/21x

b)

1/(x-3) - 1/(x+3) = [x+3-(x-3)/(x^2-9)]= 6/(x^2-9)

c)

7a^3 * 3b/14a^2 = a* 3b/2=3/2ab=1,5ab

d)

(12xy^2/5a^3 : 24y/(25a^2b) =

=12xy^2/5a^3 * 25a^2b/24y=

=xy/a *5ab/2 = 5bxy/2a

3.

a)

[x^2 +(6-x^4)/(x^2-1)] * (1+x)/(6-x^2)=

= [(x^4-x^2+6-x^4) / (x-1)(x+1) * (1+x)/(6-x^2)=

=(6-x^2)/[(x-1)(x+1)] * (x+1)/(6-x^2)= 1/(x-1)

b)

[(x+y)/3x+3) - 1/(x+1) ] : (1+x)/3 2/(1-x^2) =

=[(x+4-3)/3(x+1)] : [(1+x)/3] 2/(1-x)(1+x) =

= (x+1)/3(x+1) * 3/1+x) - 2/(1-x)(1+x)= 1/(x+1) - 2/ (1-x)(1+x)=

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