a) xy+3x-7y-21

=x(y+3)-7(x+3)

=(x-7)(y+3)

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

=2x(y-3)-5(-3+y)

=(2x-5)(y-3)

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

=2x(xy-1)+2y(xy-1)

=(2x+2y)(xy-1)

x(x+3)-5x(x-5)-5(x+3)

=(x-5)(x+3)-5x(x-5)

=(x-5)(x+3-5x)

Câu cuối mình bị nhầm dòng cuối phải là (x-5)(x+3+x-5)=(x-5)(2x-2)nha bạn

a) xy+3x-7y-21=(xy+3x)-(7y+21)= x(y+3)-7(y+3)=(y+3)(x-7)

b)2xy-15-6x+5y=(2xy-6x)+(5y-15)=2x(y-3)+5(y-3)=(y-3)(2x+5)

c)2x^2y+2xy^2-2x-2y=2xy(x+y)-2(x+y)=2(x+y)(xy-1)

d) x(x+3)-5x(x-5)-5(x+3)=[x(x+3)-5(x+3)]-5x(x-5)=(x+3)(x-5)-5x(x-5)=(x-5)(x+3-5x)=(x-5)(3-4x)

2x^2 - 6x + 5x - 15

= 2x( x-3) + 5(x-3)

=(2x + 5)(x-3)

a: \(4x^2-x-5=\left(4x-5\right)\left(x+1\right)\)

b: \(x^2-2x-15=\left(x-5\right)\left(x+3\right)\)

\(-\left(x^2+2x-15\right)=-\left(x^2+2x+1-16\right)=16-\left(x+1\right)^2=\left(17+x\right)\left(15-x\right)\)

\(x^2-2x-15\)

\(\Leftrightarrow\)\(x^2-5x+3x-15\)

\(\Leftrightarrow\)\(\left(x^2-5x\right)+\left(3x-15\right)\)

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

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

P/s:#Học Tốt#

\(2x^2-x-15=2x^2-6x+5x-15=2x\left(x-3\right)+5\left(x-3\right)=\left(x-3\right)\left(2x+5\right)\)

Đề lỗi hay sao í bạn. Bạn xem lại đề!

a) x³-2x²-x+2

=x(x²-1)+2(-x²+1)

=x(x²-1)-2(x²-1)

=(x²-1)(x-2)

b)

x²+6x-y²+9

=x²+6x+9-y²

=(x+3)²-y²

^{=(x+3-y)(x+3+y)}

\(x^2+2x-15\)

\(=x^2+5x-3x-15\)

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

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

x² + 2x - 15

= x² + 5x - 3x - 15

= x.(x+5) - 3.(x+5)

= (x+5).(x-3)

x^2+2x-15=x^2+5x-3x-15

=x(x+5)-3(x+5)=(x-3)(x+5)