Question

Help! Urgemt Constant term of (x-(2/x^2))^9
is??

I expanded it and ended up with (1)^9 and (-2)^9.
Im stuck as to wat to do from here. should i add? or... what??

Answer 1

Term(r+1) C(9,r)(x^(9-r) * (-2/x^2)^r
= C(9,r) (-2)^r * x^(9-r)x^-2r)
= C(9,r) (-2)^r * x^(9 -3r)

to have a constant term there should be no x term, that is, 9-3r = 0
r = 3

So the constant term is
C(9,3)x^3 * (-2/x^2)^3
= 84(-8) = - 672

Answer 2

second last line should have been
C(9,3)x^6 * (-2/x^2)^3

Answer 3

thnx so much!