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)

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

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

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

Tự hỏi tự trả lời rồi

Chán quá

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

tách ra thành:

(x³-x²+5x)+(x²-x+5)

=x(x²+x+5)+(x²+x+5)

=(x+1)(x²+x+5)

kq đó pn có kp qua fb vs mk la:longtrangv@gmail.com nhé

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#

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