C4 differential equations,c and A as constants

Because e^(x + c) = (e^x)e^c, and if c is a constant, then e^c is also a constant, so rewrite it as A so it looks tidier as Ae^x. Just make sure to state that A = e^c though

So I'm confused as to why we need to change the c into A? Like let's take question c, I'm assuming in the answer A=e^c but that's such a random thing to do...
I know I'm not explaining myself very well, but basically, I don't understand why u can't just keep the constant as c.