polynomial

If the product (3x^2 - 5x + 4)(7 - x) can be written in the form ax^3 + bx^2 + cx + d, where a,b,c, and d are real numbers, then find 8a + 4b + 2c + d.

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$(3x^2 - 5x + 4)(7 - x)\\ =21x^3-35x+28-3x^3+5x^2-4x\\ \color{blue}=18x^3+5x^2-39x+28$

     a           b           c          d

$\color{blue}8a + 4b + 2c + d\\ =144+20-78+28$

$=114$

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