deq1:=diff(y(x),x)=6*x+2;
dsolve(deq1,y(x));
dsolve({deq1,y(0)=5},y(x));
dsolve({deq1,y(0)=a},y(x));
deq2:=diff(y(x),x)=b*x+c;
dsolve(deq2,y(x));
seq2:=dsolve({deq2,y(0)=a},y(x));
consts:={a=5,b=6,c=3};
subseq2:=subs(consts,seq2);
rhs(subseq2);
psubseq2:=subs(subseq2,y(x));
plot(psubseq2,x=0..10);