If you look at the Debug Messages pane, the answer is spelled out: The variable $multipler is undefined because it's a typo. It should be $multiplier.
如果看一下 Debug Messages 面板，答案就清楚了：变量 $multipler 是未定义的，因为它是一个拼写错误，应该是 $multiplier。
Using the multiplier method, we study the boundary feedback stabilization of the wave equation with variable coefficient.
利用乘子法研究了带有变系数的波方程的反馈镇定问题。
The multiplier multiply said results with 10 of hexadecimal to produce No. 1 variable.
乘法器将所述减法结果乘以十六进制数‘10’，产生第一临时变量；
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