Question

Phân tích đa thức thành nhân tử 

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

Answer 1

(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)