Good, so what I have here is an equation that tells me Player 1's best response for each possible choice of Player 2.

这个方程表示,参与人2不同策略下参与人1的最佳对策

耶鲁公开课 - 博弈论课程节选

It tells me that the best response to S2 is the ?1 that solves this equation, that solves this first order condition.

我们得出S2的最佳对策是?1,?1是这个方程的解,它满足一阶条件

耶鲁公开课 - 博弈论课程节选