bn post nhiều nên mình ghi đáp án thôi nhé phần nào sai đề mình cho qua

b)\(\left(x+1\right)\left(xy+1\right)\)

c)\(\left(a+b\right)\left(x+y\right)\)

d)\(\left(x-a\right)\left(x-b\right)\)

e)\(\left(x+y\right)\left(xy-1\right)\)

f)\(\left(a-b\right)\left(x^2+y\right)\)

Ta có: \(\left(ax+by\right)^2=\left(a^2+b^2\right)\left(x^2+y^2\right)\)

\(\Leftrightarrow a^2x^2+2abxy+b^2y^2=a^2x^2+a^2y^2+x^2b^2+b^2y^2\)

\(\Leftrightarrow2abxy=a^2y^2+x^2b^2\)

\(\Leftrightarrow\left(ay-xb\right)^2=0\)

\(\Leftrightarrow ay=xb\)

hay \(\dfrac{a}{x}=\dfrac{b}{y}\)

`ab(x-3) -a^2(x-3)`

`=(x-3)(a^2-ab)`

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`ax+ay+bx+by`

`=a(x+y)+b(x+y)`

`=(x+y)(a+b)`

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`ax+ay -2x-2y`

`=(ax+ay)-(2x+2y)`

`=a(x+y)-2(x+y)`

`=(x+y)(a-2_`

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`2x-2y +ax-ay`

`=2(x-y)+a(x-y)`

`=(x-y)(2+a)`

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`10ax -5ay -2x+y`

`= 5a(2x-y) -(2x-y)`

`=(2x-y)(5a-1)`

1: =(x-3)(ab-a^2)

=a(b-a)(x-3)

2: =a(x+y)+b(x+y)

=(x+y)(a+b)

3: =a(x+y)-2(x+y)

=(x+y)(a-2)

4: =2(x-y)+a(x-y)

=(x-y)(a+2)

5: =5a(2x-y)-(2x-y)

=(2x-y)(5a-1)

1) \(ab\left(x-3\right)-a^2\left(x-3\right)=a\left(x-3\right)\left(b-a\right)\)

2) \(ax+ay+bx+by=\left(a+b\right)\left(x+y\right)\)

3) \(ax+ay-2x-2y=\left(a-2\right)\left(x+y\right)\)

4) \(2x-2y+ax-ay=\left(2+a\right)\left(x-y\right)\)

5) \(10ax-5ay-2x+y=5a\left(2x-y\right)-\left(2x-y\right)=\left(5a-1\right)\left(x-y\right)\)

\(a,=5\left(x-y\right)+a\left(x-y\right)=\left(5+a\right)\left(x-y\right)\\ b,=a\left(x+y\right)+b\left(x+y\right)=\left(a+b\right)\left(x+y\right)\\ c,=x\left(x+1\right)+a\left(x+1\right)=\left(x+a\right)\left(x+1\right)\\ d,Sửa:x^2y+xy^2-3x-3y=xy\left(x+y\right)-3\left(x+y\right)=\left(xy-3\right)\left(x+y\right)\\ e,=xy\left(x+1\right)-\left(x+1\right)=\left(xy-1\right)\left(x+1\right)\\ f,=x^2-4=\left(x-2\right)\left(x+2\right)\\ g,=\left(x+3\right)^2-y^2=\left(x-y+3\right)\left(x+y+3\right)\\ h,=\left(x+5\right)^2-y^2=\left(x-y+5\right)\left(x+y+5\right)\\ i,=\left(x-4\right)^2-24y^2=\left(x-2\sqrt{6}y-4\right)\left(x+2\sqrt{6}y+4\right)\)