Bài 16:
a) \(A-B+C\)
\(=\left(5xy^2-4x^2y-6x^2\right)-\left(8x^2y-4xy^2+3y^2\right)+\left(-2xy^2+3x^2y+5x^2\right)\)
\(=5xy^2-4x^2y-6x^2-8x^2y+4xy^2-3y^2-2xy^2+3x^2y+5x^2\)
\(=\left(5xy^2+4xy^2-2xy^2\right)-\left(4x^2y+8x^2y-3x^2y\right)-\left(6x^2-5x^2\right)-3y^2\)
\(=7xy^2-9x^2y-x^2-3y^2\)
b) \(2\left(A+B\right)+C\)
\(=2\cdot\left(5xy^2-4x^2y-6x^2+8x^2y-4xy^2+3y^2\right)+\left(-2xy^2+3x^2y+5x^2\right)\)
\(=2\cdot\left(xy^2+4x^2y-6x^2+3y^2\right)-2xy^2+3x^2y+5x^2\)
\(=2xy^2+8x^2y-12x^2+6y^2-2xy^2+3x^2y+5x^2\)
\(=11x^2y-7x^2+6y^2\)
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