1. Make s the subject of the formula
1/r = ax / x-1 + 1/s
1/s = 1/r - ax / x-1
= (x - 1 - axr) / r (x - 1)
s = r ( x-1) / (x - 1 -axr )
2. Make x the subject of the formula
1/r = ax / x-1 + 1/s (同上的)
1 / r - 1 / s = ax / x - 1
( s - r ) / rs = ax / x - 1
( s - r )( x - 1 ) = axrs
sx - rx - s + r = axrs
axrs - sx + rx = r - s
x ( ars - s + r) = r - s
x = ( r - s ) / (ars - s + r )