Question

Câu 2: Phân tích đa thức thành nhân tử:
a)4x^2+y^2-4xy
b)x^3-4x^2-12x+27

Answer 1

a, (x+2)(x−2)−(x−3)(x+1)(x+2)(x-2)-(x-3)(x+1)

=x2−4−(x2−3x+x− 3)=x2-4-(x2-3x+x- 3)

=x2− 4−x2+2x+3=x2- 4-x2+2x+3

=2x−1=2x-1

2.

a, x2−4+(x−2)2x2-4+(x-2)2

=(x−2)(x+2) +(x−2)2=(x-2)(x+2) +(x-2)2

=(x−2)(x+2+x−2)=(x-2)(x+2+x-2)

=2x(x−2)=2x(x-2)

b, x3−2x2+x−xy2x3-2x2+x-xy2

=x(x2− 2x+1−y2)=x(x2- 2x+1-y2)

=x[(x−1)2 −y2]=x[(x-1)2 -y2]

=x(x−1−y)(x−1+y)=x(x-1-y)(x-1+y)

c, x3−4x2−12x+27x3-4x2-12x+27

=(x3+27)−(4x2+12x)=(x3+27)-(4x2+12x)

=(x+3)(x2−3x+9)−4x(x+3)=(x+3)(x2-3x+9)-4x(x+3)

=(x+3)(x2−3x+9−4x)=(x+3)(x2-3x+9-4x)

=(x+3)(x2−7x+9)