a)x²+5xy²-3x²y+6xy²-2xy²+3x²y
=x²+9xy²
=x(x+9y²)
b)(5a²+3ab)+(b²-2ab)-(a²+3b²-4ab)+(a²-b²)
=5a²+3ab+b²-2ab-a²-3b²+4ab+a²-b²
=5a²+5ab-3b²
=5a(a+5b)-3b²
sau
=5a²+b(5a-3b)
c)(6m+3n)-(2n+3m+5)-(3m-4n-6)
=6m+3n-2n-3m-5+3m+4n+6
=6m+5n+1
d)(13m²+2mn-n²)-(2m²+3mn+4n²)-(10m²+2mn)
=13m²+2mn-n²-2m²-3mn-4n²-10m²-2mn
=m²-3mn-5n²