tk mình đi mình giải cho 

a) \(x^4-y^4=\left(x^2\right)^2-\left(y^2\right)^2=\left(x^2-y^2\right)\left(x^2+y^2\right)=\left(x+y\right)\left(x-y\right)\left(x^2+y^2\right)\)

c) \(36-12x+x^2=x^2-12x+36=x^2-6x-6x+36\)

\(=x\left(x-6\right)-6\left(x-6\right)=\left(x-6\right)\left(x-6\right)=\left(x-6\right)^2\)

\(x^4-y^4\)

\(=\left(x^2-y^2\right)\left(x^2+y^2\right)\)

\(=\left(x-y\right)\left(x+y\right)\left(x^2+y^2\right)\)

\(4x^2+12x+9\)

\(=\left(2x\right)^2+2.2x.3+9\)

\(=\left(2x+3\right)^2\)

\(36-12x+x^2\)

\(=6^2-2.6.x+x^2\)

\(=\left(6-x\right)^2\)

a^3+b^3+c^3-3abc

=a^3 + b^3 + 3ba^2 + 3ab^2 + b^3 - 3ab(a+b) +c^3 _ 3abc

=(a+b)^3+c^3 -3ab(a+b+c)

=(a+b+c)(a^2+2ab+b^2-bc-ca+c^2)-3ab(a+b+c)

=(a+b+c)(a^2+b^2+c^2-ab-ab-bc)

a) \(x^3\left(x^2-7\right)^2-36x=x\left[\left(x^3-7x\right)^2-6^2\right]\)

\(=x\left(x^3-7x-6\right)\left(x^3-7x+6\right)\)

\(x\left[\left(x-3\right)\left(x+1\right)\left(x+2\right)\right].\left[\left(x+3\right)\left(x-2\right)\left(x-1\right)\right]\)

\(=\left(x-3\right)\left(x-2\right)\left(x-1\right).x.\left(x+1\right)\left(x+2\right)\left(x+3\right)\)

b) Không pt được.

c) Không pt được.

\(x^4+4=x^4+4x^2+4-4x^2=\left(x^2+2\right)^2-4x^2=\left(x^2+2x+2\right)\left(x^2-2x+2\right)\)

\(4x^8+1=\left(2x^4\right)^2+1=\left(2x^4\right)^2-2.2x^4+1+2.2.x^4=\left(2x^4+1\right)^2-4x^4\)

\(=\left(2x^4+2x^2+1\right)\left(4x^4-2x^2+1\right)\)

\(x^2-8x-9==x^2+x-9x-9=x\left(x+1\right)-9\left(x+1\right)=\left(x+1\right)\left(x-9\right)\)

\(x^2+14x+48=x^2+6x+8x+48=x\left(x+6\right)+8\left(x+6\right)=\left(x+6\right)\left(x+8\right)\)

a) \(x^4+4=x^4+4x^2+4-4x^2=\left(x^2+2\right)^2-4x^2=\left(x^2+2x+2\right)\left(x^2-2x+2\right)\)

b) \(4x^8+1=\left(2x^4\right)^2+1=\left(2x^4\right)^2-2.2x^4+1+2.2.x^4=\left(2x^4+1\right)^2-4x^4\)

c) \(x^2-8x-9==x^2+x-9x-9=x\left(x+1\right)-9\left(x+1\right)=\left(x+1\right)\left(x-9\right)\)

d) \(x^2+14x+48=x^2+6x+8x+48=x\left(x+6\right)+8\left(x+6\right)=\left(x+6\right)\left(x+8\right)\)

a) \(5x^2+5xy-x-y\)

\(=5x.\left(x+y\right)-\left(x+y\right)\)

\(=\left(x+y\right)\left(5x-1\right)\)

b) \(5x^2-10y+5y^2-20z^2\)

\(=5.\left(x^2-2y+y^2-4z^2\right)\)

Đề sai ở đâu đó.

c) \(4x^2-y^2+4x+1\)

\(=\left(4x+4x^2+1\right)-y^2\)

\(=\left(2x+1\right)^2-y^2\)

\(=\left(2x+y+1\right)\left(2x-y+1\right)\)