method of variation of constant [数] 常数变易法

method of variation of parameters 参数变分法

the method of variation 变分方法

method of concomitant variation [数] 共变法

method of variation replacement 变量替换

method of variation of parameter 常数变易法

method of variation of constants 常数变易法

the method of variation coefficient 变异系数法

the method of concomitant variation 共变法 ; 附随变化法