#f(x) = (2 - 3x)/4 => f(x) = y:#
#y = (2 - 3x)/4 =># switch # x & y:#
#x = (2 - 3y)/4 =># solve for # y:#
#x/1 = (2 - 3y)/4 =># now cross multiply:
#2 - 3y = 4x =># subtract 2 from both sides:
#-3y = 4x - 2 =># divide both sides by -3:
#y = (2 - 4x)/3 =># this is the inverse function, so:
#f^-1(x) = (2 - 4x)/3#