a) M= 8xy2 - 6x2y - 3x - 14y2 - 5.
b) M= -2xy2 - 12x2y + x -5.
a) M=P+Q
M=\(\left(3x^2y-2x+5xy^2-7y^2\right)+\left(3xy^2-7y^2-9x^2y-x-5\right)\)
=\(3x^2y-2x+5xy^2-7y^2+3xy^2-7y^2-9x^2y-x-5\)
=\(\left(3x^2y-9x^2y\right)+\left(-2x-x\right)+\left(5xy^2+3xy^2\right)+\left(-7y^2-7y^2\right)-5\)
=\(-6x^2y-3x+8xy^2-14y^2-5\)
=\(8xy^2-6x^2y-14y^2-3x-5\)
b) M=Q-P
M=\(\left(3xy^2-7y^2-9x^2y-x-5\right)-\left(3x^2y-2x+5xy^2-7y^2\right)\)
=\(3xy^2-7y^2-9x^2y-x-5-3x^2y+2x-5xy^2+7y^2\)
=\(\left(3xy^2-5xy^2\right)+\left(-7y^2+7y^2\right)+\left(-9x^2y-3x^2y\right)+\left(-x+2x\right)-5\)
=\(-2xy^2-12x^2y+x-5\)
T mk nha bạn ^...^
