Write down the first three terms in the expansion, in descending powers of x, of [ax-(b/x^3)]^8. Hence evaluate the term independent of xof [5x-(1/x^3)]^8.

I dunno how to do the Hence part, making use of the terms in the expansion.

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- Oct 8th 2008, 09:00 AMmaybeline9216binomial thm
**Write down the first three terms in the expansion, in descending powers of x, of [ax-(b/x^3)]^8. Hence evaluate the term independent of x****of [5x-(1/x^3)]^8.**

I dunno how to do the Hence part, making use of the terms in the expansion. - Oct 8th 2008, 09:56 AMThePerfectHacker
In this expansion we have terms of form:

To have a term independent of we require that the in numerator cancels out the in denominator. The exponent of in numberator is and the exponent of in denominator is . We want that so that they cancel out. Therefore, if we solve this equation.

Therefore the indepentent term is: - Oct 8th 2008, 08:04 PMmaybeline9216