There are a number of apparent misconceptions lurking beneath your question. Rather than try to disentangle them, it would be better for you to give more information about why you want to know. What specific problem or scenario are you interested in? What sources are you using to understand the subject?
Light when radiated travels at exactly the same speed regardless of the speed of the source in a vacuum (the speed of the source does not enter into Maxwell's equations) so must travel at the constant speed derived above being the only speed constant in all frames.