The river water is flowing in the reverse direction.

The river water is flowing in the opposite direction.

This problem has a paradoxical answer.

He was prepared for the enemy's counterattack.

He began to strike back against the enemy.

He was plotting a rebellion against the king.

He outsmarted his competitors by using a contrarian business strategy.

He succeeded in business by going against the grain.

In order to find the inverse function, you need to solve the original function's equation for x and y.

I learned an algorithm to calculate the inverse matrix.