Mk chỉnh sửa tí nhé . Ở câu a là 2x^2 ( x-1 ) - ( 1-x ) . 4x nha
\(a,2x^2\left(x-1\right)-1\left(1-x\right)4x\)
\(=2x^2\left(x-1\right)+\left(x-1\right)4x\)
\(=\left(2x^2+4x\right)\left(x-1\right)=2x\left(x+2\right)\left(x-1\right)\)
\(b,9x^2y^2+15x^2y^3-21x^3y^2\)
\(=3x^2y^2\left(3+5y-7x\right)\)
\(c,\left(3x-1\right)^2-9\left(x+2\right)^2\)
\(=\left(3x-1\right)^2-\left[3x+6\right]^2\)
\(=\left(3x-1-3x-6\right)\left(3x-1+3x+6\right)\)
\(=-7\left(6x+5\right)\)
\(d,9-x^2-2xy-y^2\)
\(=9-\left(x+y\right)^2=\left(3-x-y\right)\left(3+x+y\right)\)
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