\(1x-0,2-\frac{1}{3}x-2+2-\frac{2}{3}x\)

\(\left(1x-\frac{1}{3}x-\frac{2}{3}x\right)-\left(0,2+2-2\right)\)

=0,2

tích đúng cho mình nhé

giải như thế nào vậy ạ ?

a) ( 4x+1) (12x-1) (3x+2) (x+1) -4

=(4x+1)(3x+2)(12x-1)(x+1)-4

=(12x²+11x+2)(12x²+11x-1)-4

Đặt t=12x²+11x+2 ta được:

t.(t-3)-4

=t²-3t-4

=t²+t-4t-4

=t.(t+1)-4.(t+1)

=(t+1)(t-4)

thay t=12x²+11x+2 ta được:

(12x²+11x+3)(12x²+11x-2)

Vậy ( 4x+1) (12x-1) (3x+2) (x+1) -4=(12x²+11x+3)(12x²+11x-2)

b) (x²+2x)²+9x²+18x+20

=(x²+2x)²+9.(x²+2x)+20

Đặt y=x²+2x ta được:

y²+9y+20

=y²+4y+5y+20

=y.(y+4)+5.(y+4)

=(y+4)(y+5)

thay y=x²+2x ta được:

(x²+2x+4)(x²+2x+5)

Vậy (x²+2x)²+9x²+18x+20=(x²+2x+4)(x²+2x+5)

4( x+5) ( x+6) (x+10) ( x+12) -3x²

=4(x+5)(x+12)(x+6)(x+10)-3x²

=4.(x²+17x+60)(x²+16x+60)-3x²

Đặt t=x²+16x+60 ta được:

4.(t+x).t-3x²

=4t²+4tx-3x²

=4t²-2tx+6tx-3x²

=2t.(2t-x)+3x.(2t-x)

=(2t-x)(2t+3x)

thay t=x²+16x+60 ta được:

[2.(x²+16x+ 60)-x][2.(x²+16x+60)+3x]

=(2x²+32x+120-x)(2x²+32x+120+3x)

=(2x²+31x+120)(2x²+35x+120)

=(2x²+16x+15x+120)(2x²+35x+120)

=[2x.(x+8)+15.(x+8)](2x²+35x+120)

=(x+8)(2x+15)(2x²+35x+120)

4( x+5) ( x+6) (x+10) ( x+12) -3x 2

=4(x+5)(x+12)(x+6)(x+10)-3x 2

=4.(x 2+17x+60)(x 2+16x+60)-3x 2

Đặt t=x 2+16x+60 ta được: 4.(t+x).t-3x 2

=4t 2+4tx-3x 2

=4t 2 -2tx+6tx-3x 2 

=2t.(2t-x)+3x.(2t-x)

=(2t-x)(2t+3x)

thay t=x 2+16x+60 ta được: [2.(x 2+16x+ 60)-x][2.(x 2+16x+60)+3x]

=(2x 2+32x+120-x)(2x 2+32x+120+3x)

=(2x 2+31x+120)(2x 2+35x+120)

=(2x 2+16x+15x+120)(2x 2+35x+120)

=[2x.(x+8)+15.(x+8)](2x 2+35x+120)

=(x+8)(2x+15)(2x 2+35x+120)

Đặt x^2 + x +1 = a 

Thay vào ta có :

a(a+1) - 12 

= a^2 + a - 12 

= a^2 + 4a - 3a - 12 

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

=(a- 3 )(a+4 )

Thay a = x^2 + x + 1 ta có :

= ( x^2 + x + 1 - 3 )(x^2 + x + 1 + 4 )

=(x^2 + x - 2 )(x^2 + x + 5 )

(4x + 1)(12x - 1)(3x + 2)(x+1) = 4

[(4x+1)(3x+2)][(12x-1)(x+1)]=4

(12x²+11x+2)(12x²+11x-1)=4

dat a=12x²+11x+2

khi do phuong trinh tro thanh:

a(a-3)=4

a²-3a-4=0

a²+a-4a-4=0

a(a+1)-4(a+1)=0

(a+1)(a-4)=0

=>a+1=0 hoac a-4=0

=>a=-1 hoac a=4

=>12x²+11x+2=-1 hoac 12x²+11x+2=4

+)12x²+11x+2=-1

=>12x²+11x+3=0

=>36x²+33x+12=0

=>36x²+33x+121/16+71/16=0

=>(6x+11/4)²=-71/16(vo li)

+)12x²+11x+2=4

=>12x²+11x-2=0

=>36x²+33x-6=0

=>36x²+33x+121/4-145/4=0

=>(6x+11/4)²=145/4

=>6x+11/4=(can 145)/2

...(tu lam tiep nha)