Q. Find the 2nd term in the expansion of (x−6y)5 in simplest form.Answer:
Use Binomial Theorem: To find the 2nd term in the expansion of (x−6y)5, we will use the binomial theorem. The general form of the k-th term in the expansion of (a+b)n is given by T(k)=C(n,k−1)⋅a(n−k+1)⋅b(k−1), where C(n,k) is the binomial coefficient "n choose k". For the 2nd term, k=2.
Calculate Binomial Coefficient: We calculate the binomial coefficient for the 2nd term, which is C(5,2−1)=C(5,1). The binomial coefficient C(n,k) is calculated as k!⋅(n−k)!n!, where “!“ denotes factorial.
Simplify Coefficient:C(5,1) is calculated as (1!∗(5−1)!)5!=(1∗4!)5=(1∗24)5=245. Since 24 is not a factor of 5, we simplify this to 5.
Calculate Powers of a and b: Now we need to calculate the powers of a and b for the 2nd term. Since a is x and b is −6y, and we are looking for the 2nd term where k=2, we have a5−2+1=x5−1=x4 and b2−1=(−6y)1=−6y.
Multiply Coefficient and Powers: Multiplying the binomial coefficient by the powers of a and b, we get the 2nd term: T(2)=C(5,1)×x4×(−6y)=5×x4×(−6y)=−30x4y.
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