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\(a.\left(3x-1\right)^2-\left(3x-2\right)\left(3x+2\right)=9x^2-6x+1-9x^2+4\)

\(=-6x+5.\)

\(b.\left(4x-3\right)^2-\left(2x+1\right)^2-\left(5x-3\right)^2\)

\(=16x^2-24x+9-4x^2-4x-1-25x^2+30x-9\)

\(=-13x^2+2x-1.\)

\(c.\left(6x-3\right)^2-\left(7x+1\right)\left(7x-1\right)=36x^2-36x+9-49x^2+1\)

\(=-13x^2-36x+10.\)

\(ab\left(x^2+y^2\right)-xy\left(a^2+b^2\right)=abx^2+aby^2-a^2xy-b^2xy\)

\(ax\left(bx-ay\right)+by\left(ay-bx\right)=\left(-ay+bx\right)\left(ax-by\right).\)

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Vãi cả bé Phạm