Why do they put letters in math?

Answer 1

Often, it's to represent numbers whose values haven't been determined yet. Sometimes, it's to represent numbers whose values are known, but take a long time to write out. For example, say you knew that a represented the value 100000000000000. Wouldn't you rather write a then 100000000000000 every time? Additionally, letters are often used to describe processes, since, once again, it's way quicker. Doesn't writing 1 + 1 sound much better than writing "one added to one," or, if you'll bear with me, wouldn't you rather write: ∂(ln(x2t+ε0))/∂t=G*∫Βx∂x instead of "the partial derivative of the natural logarithm of some unknown constant, x, raised to the power of time doubled, added to the initial value of the epsilon function, with respect to time, is equal to the universal gravitational constant multiplied by the indefinite integral of the magnitude of the magnetic field in the direction of x with respect to x"?

And yes, I just made up that equation, it's not anything theorized...until now!