a.maths question

戴維斯

binomial


in the expansion of

(x^2-2/x)^12       註: ^=次方

find the coefficient of x^9


answer:

the general term in the expansion is the (r+1) term
The (r=1)th term = 12Cr  (x^2)^12-r(-2/x)^r
                       =12Cr (-2)^r x^24-3r

                When the term contains x^9=12C5(-2)^5
                                                     =-25344


我唔明點解個笞案有數字計到出來
(x+1)^12o個o的計唔到實數

Sol_Campbell

(x+1)^12計唔到實數,計到咩

choy991044

[QUOTE=戴維斯](x+1)^12o個o的計唔到實數[/QUOTE]

??

麥旋風

因為係coefficient (系數)
which means 帶住Unknown既數字
not x 既 value
e.g︰ 3x^2-2x+4=0
X^2既coefficient就係3
x既coefficient 係 -2