if the coefficient of x to the power 4 in the expansion of (2-3px)(4x^4+5x^3-x) is 38, find the value of p.

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if the coefficient of x to the power 4 in the expansion of (2-3px)(4x^4+5x^3-x) is 38, find the value of p.

Guest May 17, 2014

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Best Answer

+130511

+8

Since only two terms in the expansion result in terms with x to the fourth power, we have

8x^4 - 3px(5x^3) =

8x^4 - 15px^4

So

(8 -15p) = 38 Subtract 8 from both sides

-15p = 30

So, p = -2

CPhill May 17, 2014

1⁺⁰ Answers

+130511

+8

Best Answer

Since only two terms in the expansion result in terms with x to the fourth power, we have

8x^4 - 3px(5x^3) =

8x^4 - 15px^4

So

(8 -15p) = 38 Subtract 8 from both sides

-15p = 30

So, p = -2

CPhill May 17, 2014

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