Question

[Vũ Thị Khánh Huyền]

Câu 1 : Thực hiện phép tính :

a) \(6x^2\left(3x^2-4x+5\right)\)

b) \(\left(3x-y\right)^2\)

c) \(\left(x+3\right)\left(x-3\right)-x\left(x-5\right)\)

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

Câu 2 : Phân tích đa thức :

a) \(14x^2y-21xy^2+28x^2y^2\)

b) \(27x^3-\dfrac{1}{27}\)

c) \(3x^2-3xy-5x+5y\)

d) \(x^2+7x+12\)

Câu 3 : Tìm x :

a) \(5x\left(x-2\right)+3x-6=0\)

b) \(x^3=9x\)

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

Answer 1

[Sáng]

Bài 1:

a, \(6x^2\left(3x^2-4x+5\right)=18x^4-24x^3+30x^2\)

b, \(\left(3x-y\right)^2=9x^2-6xy+y^2\)

c, \(\left(x+3\right)\left(x-3\right)-x\left(x-5\right)=x^2-9-x^2+5=-4\)

d, \(\left(x+2\right)^2+\left(x-3y\right)^2-\left(2x+4\right)\left(x-3\right)\)

\(=x^2+4x+4+x^2-6xy+9y^2-2x^2+2x+12\)

\(=9y^2+6x+16\)

Answer 2

[Sáng]

Bài 2:

a, \(14x^2y-21xy^2+28x^2y^2=7xy\left(2x-3y+4xy\right)\)

b, \(27x^3-\dfrac{1}{27}=\left(3x\right)^3-\left(\dfrac{1}{3}\right)^3=\left(3x-\dfrac{1}{3}\right)\left(9x^2-x+\dfrac{1}{9}\right)\)

c, \(3x^2-3xy-5x+5y=3x\left(x-y\right)-5\left(x-y\right)=\left(x-y\right)\left(3x-5\right)\)

d, \(x^2+7x+12=x^2+3x+4x+12=x\left(x+3\right)+4\left(x+3\right)=\left(x+3\right)\left(x+4\right)\)