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help in working out what to do

I have a question for homework that i just can't work out what to do
Its for binomial expansion (C2)

the first three terms in the expansion in descending powers of x of (x+k/x^2)^15
Where k is a constant are;
x^15 + 30x^12 + Ax^9

a.) find the values of k and A
b.) find the value of the term independant of x in the expansion

I have k and A
K=2 and A=420 but dont know how to do part b
I just want an explanation of how to find the answer to part b cos i really dont know what its asking me to find
Reply 1
Avatar for TenOfThem
TenOfThem
18
Original post by DawnWhisker
I have a question for homework that i just can't work out what to do
Its for binomial expansion (C2)

the first three terms in the expansion in descending powers of x of (x+k/x^2)^15
Where k is a constant are;
x^15 + 30x^12 + Ax^9

a.) find the values of k and A
b.) find the value of the term independant of x in the expansion

I have k and A
K=2 and A=420 but dont know how to do part b
I just want an explanation of how to find the answer to part b cos i really dont know what its asking me to find



Any term is xn×x−2mx^n \times x^{-2m} with a constant

You know that n + m = 15 because that is how the binomial works

You also know that this simplifies to xn−2mx^{n-2m} by laws of indices

Independent of x means the index = 0
(edited 10 years ago)
Reply 2
Avatar for DawnWhisker
DawnWhisker
OP
1
Original post by TenOfThem
Any term is xn×x−2mx^n \times x^{-2m} with a constant

You know that n + m = 15 because that is how the binomial works

You also know that this simplifies to xn−2mx^{n-2m} by laws of indices

Independent of x means the index = 0


OOh! thank you i understand now :smile: thank you!
Reply 3
Avatar for TenOfThem
TenOfThem
18
Original post by DawnWhisker
OOh! thank you i understand now :smile: thank you!


NP

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