if you take the difference of kinetic energy minus the value of G2,

如果你考虑动能减去 G2 的差值
it'll be the same.

它们将是一样的
I'm sorry, K1 - G1,

不好意思 K1 - G1
it'll be the same as K2 - G2.

等于 K2 - G2
Now, we don't like the form in which this is written.

我们不喜欢这个公式现在的形式
We have to make a little cosmetic change,

为了美观我们不得不给它一点改变
and the cosmetic change is to introduce the function U(x),

这个改变就是引入函数 U(x)
which is minus this function G(x).

也就是 - G(x)
So, once you do that,

那么一旦你做了那样的改变
you've got to remember now the force is equal to

你必须能记得所施加的力就是
minus the derivative of this function,

这个函数的导数加负号
because of the minus sign relating G to U.

因为负号把 G 和 U 联系了起来