Question

[Nguyễn Ái Thục Nhi]

Phân tích thành nhân tử :

a)xy+3x-7y-21

b)2xy-15-6x+5y

c)2x^2y+2xy^2-2x-2y

d)x^2-(a+b)x+ab

e)7x^3y-3xyz-21x^2+9z

f)4x+4y-x^2(x+y)

g)y^2+y-x^2+x

h)4x^2-2x-y^2-y

i)9x^2-25y^2-6x+10y

Answer 1

[Vũ Quang Vinh]

a) \(xy+3x-7y-21\)
\(\Leftrightarrow\left(xy+3x\right)-\left(7y+21\right)\)
\(\Leftrightarrow x\left(y+3\right)-7\left(y+3\right)\)
\(\Leftrightarrow\left(x-7\right)\left(y+3\right)\)

Answer 2

[Vũ Quang Vinh]

b) \(2xy-15-6x+5y\)
\(\Leftrightarrow\left(2xy-6x\right)-\left(15-5y\right)\)
\(\Leftrightarrow x\left(2y-6\right)-5\left(3-y\right)\)
\(\Leftrightarrow2x\left(y-3\right)+5\left(y-3\right)\)
\(\Leftrightarrow\left(2x+5\right)\left(y-3\right)\)