Given limitations of computer arithmetic, one or the other of these (eq. (3) or eq. (6)) may provide more accuracy for a particular root. When quantities of the same sign are subtracted, some loss in precision may be expected. This is a particular concern here if ac is relatively small compared to b2, in which case b has about the same magnitude as √ b2 − 4ac. This suggests that one use one of the above equations for one root, and use the other equation for the other root: