calculate similarity between curves

hello;
i have two curves that differ in length, how can i calculate the match or similarity between them

Are they both of the same type? eg so many x cubes, so many x squared and so many x's. if so, maybe you could subtract the coefficients and plot that.

eg:
y₁ = 2x²+3x-5
y₂ = 3x²-1x

then plot:
y₁-y₂ =
y= -x²+4x-5


I haven't tried this, and so it might not make any sense at all, worth a try though.

Another thing you may mean is how close the curves are in their slopes, in which case you'd do what Acidic said to the derivative of the equations.

Could you expound on what you mean by similarity?