In the binomial expansion ( - 1 / z)15 find those terms which do not depend on z. Prove identity x rightarrow (y z) = (x rightarrow y) (x rightarrow z) Prove identity A B = A B. Solution 1) expansion = 15Cn (1/z)^(n/3) * z^(15-n/2) z term power= (15-n)/2 - n/3 = 45- 3n-2n/6 = 45-5n/6= 0 n=9 9 th term has z power 0 9 th term i sindependent of z.