Binomials (2 Viewers)

[Jago]

For questions like:

Find the coefficient of x² in the expansion of (x - 1/x)⁹(x + 1/x)⁵

do i turn it into (x² - x^-2)⁹(x - 1/x)⁴ and solve? If so, HOW do i solve questions like this?

 

[brett86]

 

[Jago]

oooooh i finally see how you're doing them now, i've always been assuming that a = b. no wonder i was getting them ALL wrong. thanks