Mahery Raharinjatovo a ?crit : > hello > How can I transform this ?quation :a*x+b*y=0 to this x+(a/b)*y=0 The answer is not x+(a/b)*y=0 but x+(b/a)*y=0 One way to get it is this : (%i2) eq:a*x+b*y=0; (%o2) b*y+a*x = 0 (%i3) expand(eq/coeff(lhs(eq),x,1)); (%o3) b*y/a+x = 0 Eric Reyssat