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Find the coefficient of p^4 in the expansion of (p+3)^5*(2p-5)

This is chapter 1A of the maths methods y12 book.

What i've done so far is:

p^4*5 + 10p^3*(3)^2*[2p]
= -5p^4 + 180p^4
=175p^4

However the answer is 105 (which is from 105p^4)

I am confused as to how this answer is derived. Either im doing something wrong or ive missed a part of the mutliplaction.

I checked on my CAS and the answer is defintely 105 so its not a mistake in the book.

Thanks for answer in advanced.

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1 Answer

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Figured it out :)

5p^4*3[5] + 10p^3(3)^2*[2p]
= -5p^4 + 180p^4
=175p^4

I forgot to add the pascal triangle for the first one, and also forgot to add the second term.

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