Bài 1:

a) \(7x^2\left(x^2-5x+1\right)=7x^4-35x^3+7x^2\)

b) \(\left(2x-3\right)\left(x+7\right)=2x^2+11x-21\)

Bài 2:

a) \(4x^2y-8x^3y^2=4x^2y\left(1-2xy\right)\)

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

quên rồi

lười quá ban

a: \(A=x\sqrt{x}-y\sqrt{y}+x\sqrt{y}-y\sqrt{x}\)

\(=\left(\sqrt{x}-\sqrt{y}\right)\left(x+\sqrt{xy}+y\right)+\sqrt{xy}\left(\sqrt{x}-\sqrt{y}\right)\)

\(=\left(\sqrt{x}-\sqrt{y}\right)\left(\sqrt{x}+\sqrt{y}\right)^2\)

b: \(B=5x^2-7x\sqrt{y}+2y\)

\(=5x^2-5x\sqrt{y}-2x\sqrt{y}+2y\)

\(=5x\left(x-\sqrt{y}\right)-2\sqrt{y}\left(x-\sqrt{y}\right)\)

\(=\left(x-\sqrt{y}\right)\left(5x-2\sqrt{y}\right)\)

\(a,=7xy\left(x^2-2xy+y^2\right)=7xy\left(x-y\right)^2\\ b,=3x\left(x-y\right)-5\left(x-y\right)=\left(3x-5\right)\left(x-y\right)\\ c,=x^2+3x+4x+12=\left(x+3\right)\left(x+4\right)\)

12x² + 7x - 12

= 12x² + 16x - 9x - 12

= 4x.( 3x + 4 ) - 3.( 3x + 4 )

= ( 3x + 4 ).( 4x - 3 )

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

\(=12x^2+16x-9x-12\) 

\(=4x\left(3x+4\right)-3\left(3x+4\right)\)

\(=\left(4x-3\right)\left(3x+4\right)\)

a,( x⁴-x³)-(x²-1)

=x³(x-1)-(x-1)(x+1)

=(x³-x-1)(x-1)

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chỉnh lại đề nè:không có chữ chung nhé

Mk mới lớp 7 thui nên mình ko làm đc bài này.