3(a-5)=2(2a+9)
7(b-3)=2(b+12)
10(a-5)=6(a-3)
4(x+3)+m(x+3)
3(c-5)=4(c+2)
del (1/r)= -r/r^3 where r = (x^2+y^2+z^2)^-1/2
6xy+10x^2y
27-3a=5a+1-16a