Maths ratinoal functions

[2x^(2)-18]/[x^(4)-81]

3.Simplify each of the following expression.
a.[x^(2)-2x+1]/[3x^(2)+17x-28]除以{[1-x^(2)]/[-3x^(2)+25x-28]}
b.[(3m-21n)/(6m+12n)]^2除以{[m^(2)n-49n^(3)]/[2m^(2)+8mn+8n^(2)] 乘以{[m^(2)n^(2)]/m^(2)-7mn]}

4.Let P(x)=[x^(4)-1]/[x^(3)-1] and Q(x)={[x^(2)+1](x+1)}/[x^(2)+x+1].
Do P(x) and Q(x) represent the same rational function?Explain your answer.

5.Let a>b>0.A solid metal cuboid of base area[a^(3)-b^(3)]cm2 and height(a+b)cm is melted
and recast into a new solid cuboid.If the base area of the new cuboid is [a^(2)-b^(2)]cm2,express
the height of the new cuboid in terms of a and b.

6.Let P=x^(3)-x^(2)-20x and Q=x^(3)+3x^(2)-24x-80.Find the HCF of P and Q.

7.Let R=3x^(3)+2x^(2)+1 and S=3x^(3)-7x^(2)+3x-2.Find the LCM of R and S.

8.Let f(x)=36x^(2)-12x-24 and g(x)=f(x)+3x^(3)-34x^(2)+16
a.Find g(x).
b.Find the HCF of f(x) and v(x)

9.Let u(x)=3x^(3)-2x^(2)-19x-6 and v(x)=-x[u(x)-6x^(3)+16x^(2)+6x
a.Find v(x)
b.Find the LCM of u(x) and v(x)

10.Let f(x)=2x^(3)-x^(2)-x and g(x)=2x^(3)-3x^(2)+1
a.Find the value of g(1).Hence,factorize g(x)
b.Let P and Q be the HCF and LCM of f(x) and g(x) respectively.
i.Find P and Q.
ii.Are the results of f(x)g(x) and P x Q equal?Explain your answer.

11.Let R=x^(4)-y^(4) and S=x^(3)y-x^(2)y-xy^(3)+y^3
a.Find the HCF and LCM of R and S.
b.Using the results of (a),find R x S.

12.The HCF and LCM of two polynomials are x^(2)y and 3x^(3)y^(2)z respectively.If the first polynomial is x^(2)y^(2),
find the second polynomial.

13.The HCF and LCM of three polynomials are bc and a^(2)b^(4)c^(3) respectively.If the first and the second
polynomials are abc^(3) and a^(2)bc^(2) respectively,find the third polynomial.

14.The HCF and LCM of three polynomials P,Q and R are 6uv^(2) and 72u^(3)v^(3)w^(2) respectively,where P=12uv^(2)
and Q=24u^(2)v^(2)w^(2).Write down two possible polynomials of R.

唔該show埋steps，最好跟番平時考試的要求。
同埋Ed題目我真係唔識，所以先問，唔係因為懶而問，所以唔好誤會。