Infinity is the force when we're thinking about it and our brains, negative infinity is when we actually plug it into the equation here, and the reason is the convention that the negative sign is just telling us the direction that the force is coming together instead of pushing apart.

说力有多大时，我们想到的,是无穷大，而方程解出来的,是负无穷，这是因为习惯上,我们用负号表示力的方向,是相互吸引而不是相互排斥的,所以我们可以用库仑定律。

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It says, if you pull it to the right, so that x is positive, the spring will exert a force which is in the negative direction; that's why you have a minus sign.

就是说,如果你向右拉,x 取正值,弹簧产生的力方向为负,这就是这里用负号的原因

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