a) =2x²-x+14x-7=2x²+13x-7
b)=2a²+8a-a-4=2a²+7a-4
c)=8a-12a²-2+3a=-12a²+11a-2
d)=a^6+a^5-a-1
e)=4k^3+2k²-2k-1
f)=3p²+3-p^5-p^3
