Coefficient
 Usage
• Coefficient[expr, form]给出了多项式expr中form的系数。
• Coefficient[expr, form, n]给出了expr中 form^n 的系数。
Notes
• Coefficient 仅挑选指定特定形式的项。  并不看作  的部分. • form 可以是幂的乘积。 • Coefficient[expr, form, 0]挑选与form不成比例的项。 • 无论expr是否明确以扩展形式给出，Coefficient都是有效的。
 Further Examples
Here is one way of getting the coefficient of  from the polynomial.
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Here is an equivalent way.
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This gives the coefficient of x in the polynomial over the integers modulo  .
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This gives the coefficients of x, x z, y and z in the expression.
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You can use variables that are powers.
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Such a power does not necessarily have to be an integer.
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Coefficient is quite fast for polynomial input. (The time will vary for different machines.)
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Even this harder example comes back in reasonable time.
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Coefficient can handle some algebraic dependencies.
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