How to adjust alignment within Math ($$)?

[Andrew]

@Ethan_Pixar

$ cases(
&2&y_1 &+ &y_2 &= x_1\
& &y_1 &+ 2&y_2 &= x_2\
-&2&y_1 &+ 3&y_2 &= x_3
) $

You don’t have to use the alignment point after everything, you can use only the amount that is enough for it to look good. Additionally, in cases you should use , as a case delimiter (instead of using explicit line breaks):

$ cases(
   &2&y_1 +  &y_2 = x_1,
   & &y_1 + 2&y_2 = x_2,
  -&2&y_1 + 3&y_2 = x_3,
) $

@Ethan_Pixar

$ cases(
    &1 + 2^3 + 3^3 + 4^4
	&= 4a_1 + 4^2a_2 + 4^3a_3 + 4^4a_4\

    &1 + 2^3 + 3^3
	&= 3a_1 + 3^2a_2 + 3^3a_3 + 3^4a_4\

	&1 + 2^3
	&= 2a_1 + 2^2a_2 + 2^3a_3 + 2^4a_4\
	
	&1
	&=  op(" ")a_1 +   op(" ")op(" ")a_2 +   op(" ")op(" ")a_3 +   op(" ")op(" ")a_4
) $

I’d argue that using op creates unnecessary complexity in code and it’s better to insert a few alignment point in previous cases:

$ cases(
  & 1 + 2^3 + 3^3 + 4^4
  & = 4 & a_1 + 4^2 & a_2 + 4^3 & a_3 + 4^4 & a_4,
    
  & 1 + 2^3 + 3^3
  & = 3 & a_1 + 3^2 & a_2 + 3^3 & a_3 + 3^4 & a_4,
    
  & 1 + 2^3
  & = 2 & a_1 + 2^2 & a_2 + 2^3 & a_3 + 2^4 & a_4,
    
  & 1
  & =   & a_1 +     & a_2 +     & a_3 +     & a_4,
) $

Note that you can also add spaces in the code to make source more readable too.