\(3x^2-3y^2-2\left(x-y\right)^2\)

\(=3\left(x^2-y^2\right)-2\left(x-y\right)^2\)

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

\(=\left(x-y\right)\left[3\left(x+y\right)-2\left(x-y\right)\right]\)

\(=\left(x-y\right)\left(3x+3y-2x+2y\right)\)

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

x² - 3x + 3y - y²

= (x² - y²) - (3x - 3y)

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

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

= x² - y² - 3x+3y = (x-y)(x+y) -3(x-y)

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

nhớ chọn cho mk nha!!!!!!

x²-y²-3x+3y

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

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

=(x^2-2xy-y^2)-(3x-3y)

=(x-y)^2-3(x-y)

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

\(9\left(x+1\right)^2-\left(3x-2\right)^2\)

\(=9\left(x^2+2x+1\right)-\left(9x^2-12x+4\right)\)

\(=9x^2+18x+9-9x^2+12x-4\)

\(=30x+5\)

\(=5\left(6x+1\right)\)

\(9\left(x+1\right)^2-\left(3x-2\right)^2\)

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

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

\(=5\left(6x+1\right)\)

\(9\left(x+1\right)^2-\left(3x-2\right)^2\)

=\(\left(9x^2+18x+9\right)-\left(9x^2-12x+4\right)\)

=\(9x^2+18x+9-9x^2+12x-4\)

=\(5\left(6x+1\right)\)

MHƯ VẬY ĐÚNG KHÔNG

Ta có (x^2 + y^2 )^3 + (z^2 – x^2 )^3 – (y^2 + z^2 )^3

= (x^2 + y^2 )^3 + (z^2 – x^2 )^3 + (-y^2 - z^2 )^3

Ta thấy x^2 + y^2 + z^2 – x^2 – y^2 – z^2 = 0

=> áp dụng nhận xét ta có: (x^2+y^2 )^3+ (z^2 -x^2 )^3 -y^2 -z^2 )^3

= 3(x^2 + y^2 ) (z^2 –x^2 ) (-y^2 – z^2 )

= 3(x^2+y^2 ) (x+z)(x-z)(y^2+z^2 )

Đặt \(A=\left(x-y+4\right)^2-\left(3x+3y-1\right)^2\)

Ta có:

\(\left(x-y+4\right)^2=x^2-xy+4x-yx+y^2-4y+4x-4y+16\)

                          \(=x^2+y^2-2xy+8x-8y+16\)

\(\left(3x+3y-1\right)^2=9x^2+9xy-3x+9xy+9y^2-3y-3x-3y+1\)

                               \(=9x^2+9y^2-6x-6y+18xy+1\)

Mình làm đến đây bạn trừ 2 kết quả cho nhau rồi sẽ ra

Câu a :

\(\left(x-5\right)^2+\left(x-5\right)\left(x+5\right)-\left(5-x\right)\left(2x+1\right)\)

\(=x^2-10x+25+x^2-25-10x-5+2x^2+x\)

\(=4x^2-19x-5\)

Câu b :

\(\left(3x-2\right)\left(4x-3\right)-\left(2-3x\right)\left(x-1\right)-2\left(3x-2\right)\left(x+1\right)\)

\(=12x^2-9x-8x+6-2x+2+3x^2-3x-6x^2-6x+4x+4\)

\(=9x^2-24x+2\)