x3y3−5x3y5+9y2−8 find coeifecient

Question

x3y3−5x3y5+9y2−8
find coeifecient

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Diễm Kiều 4 years 2021-08-27T05:45:35+00:00 1 Answers 10 views 0

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  1. bonexptip
    0
    2021-08-27T05:46:36+00:00
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    Answer:

    The coefficient is 90.

    Step-by-step explanation:

    Expansion of (a+b)n gives us (n+1) terms which are given by

    binomial expansion xnCra(n−r)br, where r ranges from n to 0.

    Note that powers of a and b add up to n and in the given problem this n=5.

    In (x−3y)5, we need coefficient of x3y2, we have 3rd power of x and as such r=5−3=2

    and as such the desired coefficient of x3y2 is given by

    x5C2x(5−2)(−3y)2=5×41×2×3(−3y)2

    = 10×3×9y2=90x3y2

    Hence, the coefficient of x3y2 in (x−3y)5 is 

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