1: 2a+2b=2(a+b)

2: 2a+4b+6c

=2*a+2*2b+2*3c

=2(a+2b+3c)

3: \(-7a-14ab-21b=-7\left(a+2ab+3b\right)\)

4: \(2ax-2ay+2a=2a\left(x-y+1\right)\)

5: \(=3a\cdot ax-3a\cdot2ay+3a\cdot4=3a\left(ax-2ay+4\right)\)

6: \(=2\cdot2ax-2\cdot ay-2\cdot1=2\cdot\left(2ax-ay-1\right)\)

7: =a^2-(2b)^2

=(a-2b)(a+2b)

8: =(5a)^2-1^2

=(5a-1)(5a+1)

9: =9(16a^2-9)

=9(4a-3)(4a+3)

câu 1 B 

câu 2 D

câu 3 ko bt 

câu 4 x=-1/2; x = -(căn bậc hai(3)*i-1)/4;x = (căn bậc hai(3)*i+1)/4;

câu 5 x=-5/3, x=0, x=1

Câu 1:  x² + 2 xy + y²   bằng:

A. x² + y²                   B.(x + y)²                  C. y² – x²                  D. x² – y²

Câu 2:  (4x + 2)(4x – 2)  bằng:

A. 4x² + 4                  B. 4x² – 4                 C. 16x² + 4                D. 16x² – 4

Câu 3: 25a²  + 9b²  - 30ab  bằng:

A.(5a-9b)²                  B.(5a – 3b)²              C.(5a+3b)²                D.(5a)² – (3b)²

Câu 4: 8x³ +1 bằng

A.(2x+1).(4x²-2x+1)      B. (2x-1).(4x²+2x+1)       C.(2x+1)³            D.(2x)³-1³

Câu 5:Thực hiện phép nhân  x(3x² + 2x - 5) ta được:

A.3x³ - 2x² – 5x          B. 3x³ + 2x² – 5x      C. 3x³ - 2x² +5x         D. 3x³ + 2x² + 5x

\(6x^3-9x^2=3x^2\left(2x-3\right)\\ 25x^2-0,09=\left(5x-0,3\right)\left(5x+0,3\right)\\ x^2-x-y^2-y=\left(x-y\right)\left(x+y\right)-\left(x+y\right)=\left(x+y\right)\left(x-y-1\right)\\ \left(x^2+4\right)^2-16x^2=\left(x^2-4x+4\right)\left(x^2+4x+4\right)=\left(x-2\right)^2\left(x+2\right)^2\)

bạn tách ra từng ít câu 1 thôi ạ

a: \(=5x\left(xy^2+3x+6y^2\right)\)

b: \(=\left(x-2\right)\left(x+3\right)-\left(x-2\right)\left(x+2\right)=\left(x-2\right)\left(x+3-x-2\right)=\left(x-2\right)\)

c: \(=\left(x-3\right)\left(x-4\right)\)

d: \(=x\left(x^2-2xy+y^2-9\right)\)

=x(x-y-3)(x-y+3)

e: \(=\left(x+y\right)^2-25=\left(x+y+5\right)\left(x+y-5\right)\)

f: \(=\left(x-4\right)\left(x+3\right)\)

`A=16x^2+8x+5`

`=16x^2+8x+1+4`

`=(4x+1)^2+4>=4`

Dấu "=" xảy ra khi `4x+1=0<=>x=-1/4`

`B=x^2-x`

`=x^2-x+1/4-1/4`

`=(x-1/2)^2-1/4>=-1/4`

Dấu "=" xảy ra khi `x=1/2`

`C=a^2-2a+b^2+6b+2021`

`=a^2-2a+1+b^2+6b+9+2011`

`=(a-1)^2+(b+3)^2+2011>=2011`

Dấu "=" xảy ra khi \(\begin{cases}a=1\\b=-3\\\end{cases}\)

Bài 1: 

a: \(11x^2-6xy-5y^2\)

\(=11x^2-11xy+5xy-5y^2\)

\(=11x\left(x-y\right)+5y\left(x-y\right)\)

\(=\left(x-y\right)\left(11x+5y\right)\)

b: \(4x^3-16x^2+19x-6\)

\(=4x^3-8x^2-8x^2+16x+3x-6\)

\(=\left(x-2\right)\left(4x^2-8x+3\right)\)

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

Bài 1: 

a: \(11x^2-6xy-5y^2\)

\(=11x^2-11xy+5xy-5y^2\)

\(=11x\left(x-y\right)+5y\left(x-y\right)\)

\(=\left(x-y\right)\left(11x+5y\right)\)

b: \(4x^3-16x^2+19x-6\)

\(=4x^3-8x^2-8x^2+16x+3x-6\)

\(=\left(x-2\right)\left(4x^2-8x+3\right)\)

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

\(a,=11x^2-11xy+5xy-5y^2=\left(11x+5y\right)\left(x-y\right)\\ b,=4x^3-8x^2-8x^2+16x+3x-6\\ =\left(x-2\right)\left(4x^2-8x+3\right)\\ =\left(x-2\right)\left(4x^2-2x-6x+3\right)\\ =\left(x-2\right)\left(2x-1\right)\left(2x-3\right)\)

Bài 1: 

a: \(11x^2-6xy-5y^2\)

\(=11x^2-11xy+5xy-5y^2\)

\(=11x\left(x-y\right)+5y\left(x-y\right)\)

\(=\left(x-y\right)\left(11x+5y\right)\)

b: \(4x^3-16x^2+19x-6\)

\(=4x^3-8x^2-8x^2+16x+3x-6\)

\(=\left(x-2\right)\left(4x^2-8x+3\right)\)

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