Mấy câu dễ mình làm trước nhé. Mấy câu khó hơn mình trình bày sau :)

1) 2x² - 5xy - 3y² = 2x² + xy - 6xy - 3y² = x( 2x + y ) - 3y( 2x + y ) = ( 2x + y )( x - 3y )

2) 7x² + 3xy - 10y² = 7x² - 7xy + 10xy - 10y² = 7x( x - y ) + 10y( x - y ) = ( x - y )( 7x + 10y )

3) x² + 5x - 2 = ( x² + 5x + 25/4 ) - 33/4 = ( x + 5/2 )² - \(\left(\frac{\sqrt{33}}{2}\right)^2\)= \(\left(x+\frac{5}{2}-\frac{\sqrt{33}}{2}\right)\left(x+\frac{5}{2}+\frac{\sqrt{33}}{2}\right)\)

6) x⁴ + 324 = ( x⁴ + 36x² + 324 ) - 36x² = ( x² + 18 )² - ( 6x )² = ( x² - 6x + 18 )( x² + 6x + 18 )

4) x⁸ + x⁷ + 1

= x⁸ + x⁷ + x⁶ - x⁶ + 1

= x⁶( x² + x + 1 ) - ( x⁶ - 1 )

= x⁶( x² + x + 1 ) - ( x³ - 1 )( x³ + 1 )

= x⁶( x² + x + 1 ) - ( x - 1 )( x² + x + 1 )( x³ + 1 )

= ( x² + x + 1 )( x⁶ - ( x - 1 )( x³ + 1 ) ]

= ( x² + x + 1 )( x⁶ - x⁴ + x³ - x + 1 )

5) x⁷ + x⁵ + 1

= x⁷ + x⁶ - x⁶ + x⁵ + 1

= x⁵( x² + x + 1 ) - ( x⁶ - 1 )

= x⁵( x² + x + 1 ) - ( x³ - 1 )( x³ + 1 )

= x⁵( x² + x + 1 ) - ( x - 1 )( x² + x + 1 )( x³ + 1 )

= ( x² + x + 1 )[ x⁵ - ( x - 1 )( x³ + 1 ) ]

= ( x² + x + 1 )( x⁵ - x⁴ + x³ - x + 1 )

7) x⁵ - 5x³ + 4x

= x⁵ - x³ - 4x³ + 4x

= x³( x² - 1 ) - 4x( x² - 1 )

= ( x² - 1 )( x³ - 4x )

= ( x - 1 )( x + 1 )x( x² - 4 )

= x( x - 1 )( x + 1 )( x - 2 )( x + 2 )

8) Xin hàng :)

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

e: \(=\left(x-2\right)\left(x-3\right)\)

a) x(4y-10x)

b)3(x+2y)+(x+1)

c)(5x-y)(5x+y)

d)5x(y-z)²

e)(x-3)(x-2)

f)(2x+y)³

\(=2ab\left(2b+a\right)\left(y+x\right)\)

\(x^5-4x^3-5x\)

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

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

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

\(=x\left(x^2+1\right)\left(x+\sqrt{5}\right)\left(x-\sqrt{5}\right)\)

a/

\(a^4+b^4+c^4-2a^2b^2-2b^2c^2-2c^2a^2.\)

=>\(a^4+b^4+c^4-2\left(ab\right)^2-2\left(bc\right)^2-2\left(ac\right)^2\) 

=>\(a^4+b^4+c^4-2\left(ab\right)^2-2\left(bc\right)^2+2\left(ac\right)^2-4\left(ca\right)^2\)

áp dụng hằng đẳng thức  \(a^2-b^2-c^2=a^4+b^4+c^4-2\left(ab\right)^2-2\left(bc\right)^2+2\left(ac\right)^2\) ta đc

\(\left(a^2-b^2+c^2\right)-4\left(ac\right)^2\)

=> \(\left(a^2-b^2+c^2-2ac\right)\left(a^2-b^2+c^2+2ac\right)\)

\(x^5-4x^3-5x=x\left(x^4-4x^2-5\right)\)

a)

=4x(x²+2)

b)

= (3x-y)²-7²

= (3x-y-7)(3x-y+7)

c)

= (5x²-10x)-(5xy-10y)

= 5x(x-2)-5y(x-2)

=(x-2)(5x-5y)

=5(x-2)(x-y)

a, \(\left(x+1\right)^2-2\left(x+1\right)\left(y-3\right)+\left(y-3\right)^2=\left[\left(x+1\right)-\left(y-3\right)\right]^2\)

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

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

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

a: \(x^2-9-x^2\left(x^2-9\right)\)

\(=\left(x^2-9\right)-x^2\left(x^2-9\right)\)

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

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

b: \(x^2\left(x-y\right)+y^2\left(y-x\right)\)

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

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

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

c: \(x^3+27+\left(x+3\right)\left(x-9\right)\)

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

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

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

d: \(x^2+5x+6\)

\(=x^2+2x+3x+6\)

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

e: \(3x^2-4x-4\)

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

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

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

g: \(x^4+64y^4\)

\(=x^4+16x^2y^2+64y^4-16x^2y^2\)

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

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

h: \(a^2+b^2+2a-2b-2ab\)

\(=a^2-2ab+b^2+2a-2b\)

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

i: \(\left(x+1\right)^2-2\left(x+1\right)\left(y-3\right)+\left(y-3\right)^2\)

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

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

k: \(x^2\left(x+1\right)-2x\left(x+1\right)+\left(x+1\right)\)

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

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

\(a,=\left(xy-1-x-y\right)\left(xy-1+x+y\right)\\ b,Sửa:a^3+2a^2+2a+1\\ =a^3+a^2+a^2+a+a+1=\left(a+1\right)\left(a^2+a+1\right)\\ c,=1-4a^2-a\left(a^2-4\right)=1-4a^2-a^3+4a\\ =\left(1-a\right)\left(1+a+a^2\right)+4a\left(1-a\right)\\ =\left(1-a\right)\left(1+5a+a^2\right)\\ d,=\left(a^2-a^2b^2\right)+\left(b^2-b\right)+\left(ab-a\right)\\ =a^2\left(1-b\right)\left(1+b\right)+b\left(b-1\right)+a\left(b-1\right)\\ =\left(b-1\right)\left(-a^2-ab+b+a\right)\\ =\left(b-1\right)\left(b-1\right)\left(a+b\right)\left(1-a\right)\)

\(e,=x^2y+xy^2-yz\left(y+z\right)+x^2z-xz^2\\ =\left(x^2y+x^2z\right)+\left(xy^2-xz^2\right)-yz\left(y+z\right)\\ =x^2\left(y+z\right)+x\left(y-z\right)\left(y+z\right)-yz\left(y+z\right)\\ =\left(y+z\right)\left(x^2+xy-xz-yz\right)\\ =\left(y+z\right)\left(x+y\right)\left(x-z\right)\)

\(f,=xyz-xy-yz-xz+x+y+z-1\\ =xy\left(z-1\right)-y\left(z-1\right)-x\left(z-1\right)+\left(x-1\right)\\ =\left(z-1\right)\left(xy-y-x+1\right)=\left(z-1\right)\left(x-1\right)\left(y-1\right)\)

4a²b² + 36a²b³ + 6ab⁴

= 2ab²(2a + 18ab + 3b²)

3n(m - 3) + 5m(m - 3)

= (3n + 5m)(m - 3)

2a(x - y) - (y - x)

= (x - y)(2a + 1)

4a²b³ - 6a³b²

= 2a²b²(2b - 3a)