Explicación paso a paso:}
1.
[tex]3x^{2} - 6x+8-x^{2} +9x-2+x^{2} -3x+1[/tex]
[tex]3x^{2} - 6x+8 +9x-2 -3x+1\\3x^{2} + 7[/tex]
2.
[tex]3y^{3}-2y^{2}+ 3y-2-y^{3}+5y^{2}+ 8y-2+3y^{3} -2y^{2}\\5y^{3}+11y+4y^{2}-4[/tex]
3.
[tex]6m^{2} +5mn-3n^{2}-7mn+n^{2}-8m^{2}+5n^{2} \\2m^{2}-2mn-6n^{2}[/tex]
4.
[tex]6ab+8a^{3}-3a^{2}b+9ab-7a^{2} -2a^{2}b+5ab\\20ab+8a^{3}-5a^{2}b[/tex]
5.
[tex]8xy-5x^{3}+5y^{3}-7x^{2}y+8xy^{2}-3xy^{2}+3xy-2x^{2}y\\11xy-5x^{3}+5y^{3}-9x^{2}y+5xy^{2}[/tex]
6.
[tex]3mn+3m^{3} -6n^{3} +8m^{2}n- 5mn^{2}+6mn-3m^{2}n+2\\9mn+3m^{3} -6n^{3}+2[/tex]
