1) с^2-3c+2c-6=c^2-c-6
2) 6a^2+8a-3a-4=6a^2+5a-4
3) 20x^2-5xy-8xy-2y^2=20x^2-113xy-2y^2
4) a^3-3a^2+6a-2a^2+6a-12=a^3-5a^2+12a-12
1) с^2-3c+2c-6=c^2-c-6
2) 6a^2+8a-3a-4=6a^2+5a-4
3) 20x^2-5xy-8xy-2y^2=20x^2-113xy-2y^2
4) a^3-3a^2+6a-2a^2+6a-12=a^3-5a^2+12a-12