Giúp mình với 

a ) ( 3x² + 3x + 2)² - ( 3x² + 3x - 2)²

=(3x² + 3x + 2 + 3x² + 3x - 2) [( 3x² + 3x + 2) - ( 3x² + 3x - 2) ]

=(6x²+6x)*4

=24x(x+1)

b ) ( xy+1)² - ( x+y)²

=( xy+1 + x+y ) [( xy+1) - ( x+y)]

=[x(y+1)+(y+1)] [x(y-1) - (y-1)] 

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

c ) ( x + y)³ - ( x - y)³

=[( x + y)-( x - y)] [( x + y)² -  ( x + y)( x - y) + ( x - y)² ] 

=2y( x²+2xy+y² - x²+y²+ x²-2xy +y² )

=2y(3y²+x²)

d ) 4( x² - y² ) - 8(x - ay) - 4(a² - 1)

=4(-a²+2ay-y²+x²-2x+1)

=4[-(a-y)²+(x-1)²]

=-4(y-x-a+1)(y+x-a-1)

có 3 loại xe 12 chỗ và 4 xe loại 7 chỗ

a) 4x²+3y²-4x+30y+78

=4x²-4x+1+3y²+30y+75+2

=(4x²-4x+1)+3(y²+10y+25)+2

=(2x-1)²+3(y+5)²+2>0 với mọi x

=>ko có x;y nào thỏa mãn

b)3x²+6y²-12x-20y+40

\(=3\left(x^2-4x+4\right)+6\left(y^2-\frac{10}{3}+\frac{25}{9}\right)+\frac{34}{3}\)

\(=3\left(x-2\right)^2+6\left(y-\frac{5}{3}\right)^2+\frac{34}{3}>0\) với mọi x

=>ko có x;y nào thỏa mãn

con này dễ mà

x³ + 2x² - 6x - 27

= (x³ - 3x²) + (5x² - 15x) + (9x - 27)

= x²(x - 3) + 5x(x - 3) + 9(x - 3)

= (x - 3)(x² + 5x + 9)   

ket ban nha

10^n tan cung la 1 ...

18n - 1 chia het cho 9, tan cung la -1 ...

=> 1 + (-1) = 0 chia het cho 27

Hieu thi tu lam

Khong hieu thi ke :D

-.-

\(3x^2-16x-35\)

\(=3x^2-21x+5x-35\)

\(=3x\left(x-7\right)+5\left(x-7\right)\)

\(=\left(3x+5\right)\left(x-7\right)\)

1) \(6x^2-15x+6\) 

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

\(=3x\left(2x-1\right)-6\left(2x-1\right)\)

\(=\left(3x-6\right)\left(2x-1\right)\)

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

b) \(6x^2-20x+6\) 

\(=6x^2-2x-18x+6\)

\(=2x\left(3x-1\right)-6\left(3x-1\right)\)

\(=\left(2x-6\right)\left(3x-1\right)\)

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

c) \(-10x^2-7x+6\)

\(=5x-10x^2+6-12x\)

\(=5x\left(1-2x\right)+6\left(1-2x\right)\)

\(=\left(5x+6\right)\left(1-2x\right)\)

d) \(10x^2-7x-12\)

\(=10x^2-15x+8x-12\)

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

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

1) 6x^2 - 15x + 6

= 6x^2 - 12x - 3x +6

= 6x (x - 2) - 3 (x - 2)

= (x - 2) (6x - 3)

= 3 (x - 2) (x - 1)

2) 6x^2 - 20x + 6

= 6x^2 - 18x - 2x + 6

= 6x (x - 3) - 2 (x - 3)

= (x - 3) (6x - 2)

= 2 (x - 3) (3x - 1)

3) -10x^2 - 7x + 6

= -10x^2 + 5x - 12x + 6

= 5x (1 - 2x) + 6 (1 - 2x)

= (1 - 2x) (5x + 6)

4) 10x^2 - 7x - 12

= 10x^2 - 15x + 8x - 12

= 5x (2x - 3) + 4 (2x - 3)

= (2x - 3) (5x + 4)

good luck !