This is an inline \(a^*=x-b^*\) equation.

These are block equations:

\[a^*=x-b^*\]\[ a^*=x-b^* \]\[ a^*=x-b^* \]

These are also block equations:

$$a^*=x-b^*$$$$ a^*=x-b^* $$$$ a^*=x-b^* $$