\(A=n^4-6n^3+27n^2-54n+32\)

\(=\left(n^4-3n^3+16n^2\right)-\left(3n^3-9n^2+48n\right)+\left(2n^2-6n+32\right)\)

\(=n^2\left(n^2-3n+16\right)-3n\left(n^2-3n+16\right)+2\left(n^2-3n+16\right)\)

\(=\left(n^2-3n+2\right)\left(n^2-3n+16\right)\)

\(=\left(n-2\right)\left(n-1\right)\left(n^2-3n+16\right)\)

Nhận thấy:  \(\left(n-2\right)\left(n-1\right)\)là tích 2 số nguyên liên tiếp    \(\left(n\in Z\right)\)

=>  \( \left(n-2\right)\left(n-1\right)\)\(⋮\)\(2\)

=>  A chia hết cho 2

      \(2x^2-8y^2+5xy^2-10y^3\)

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

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

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

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

      \(3x^3-12x^2y+12-75xz^2\)

\(=3\left[x^3-4x^2y+4-25xz^2\right]\)

4x(x-2005)-(x+2005)=0

4x(x-2005)+(x-2005)=0

(x-2005)(4x+1)=0

<=>x-2005=>x=2005

4x+1=0=>x=-1/4

b, (x+1)²-x-1=0

(x+1)²-(x+1)=0

(x+1)(x+1-1)=0

(x+1)x=0

<=>x+1=0=>x=-1

x =0

1. A: Who are you friends ?

    B: It's Mai

2. A: What are you good at?

    B: It's information technology

3. A: What is your favourite thing ?

    B: My favorite thing is Teddy Bear

It's Vo Phuoc Toan

It's caculator Math

It's study

Hope you good study!

\(5x.\left(x-10\right)-2x+2x+20\)

\(=5x^2-50x+20\)

\(=5\left(x^2-10x+5^2-21\right)\)

\(=5\left[\left(x-5\right)^2-\left(\sqrt{21}\right)^2\right]\)

\(=5\left(x-5-\sqrt{21}\right)\left(x-5+\sqrt{21}\right)\)

\(a\left(a-b\right)^2\left(a+b\right)-\left(b-a\right)^2\left(a^2-5ab+b^2\right)\)

\(=a\left(a-b\right)^2\left(a+b\right)-\left(a-b\right)^2\left(a^2-5ab+b^2\right)\)

\(=\left(a-b\right)^2\left[a.\left(a+b\right)-a^2+5ab-b^2\right]\)

\(=\left(a-b\right)^2\left[a^2+ab-a^2+5ab-b^2\right]\)

\(=\left(a-b\right)^2\left(6ab-b^2\right)\)

Sửa đề: \(\left(a-b\right)^2-\left(b-a\right)\left(a-3b\right)\)

\(=\left(a-b\right)^2+\left(a-b\right)\left(a-3b\right)\)

\(=\left(a-b\right)\left(a-b+a-3b\right)\)

\(=\left(a-b\right)\left(2a-4b\right)\)

\(=2.\left(a-b\right)\left(a-2b\right)\)

Tham khảo nhé~

1 because nha bn

I'm going to study hard because i want to get good marks .

Cứ dịch nghĩa là xong ..

~~~~~~~~~~~~~~~~~~~~~~~

a) because

b) so

c) so