Q. Find the 3 rd term in the expansion of (3x+y)6 in simplest form.Answer:
Identify Binomial Expansion Form: Identify the general form of the binomial expansion.The binomial theorem states that the expansion of (a+b)n will have terms of the form C(n,k)⋅a(n−k)⋅bk, where C(n,k) is the binomial coefficient, which can be calculated using the formula C(n,k)=k!⋅(n−k)!n!.
Determine Specific Term: Determine the specific term we are looking for.We are looking for the 3rd term in the expansion, which corresponds to k=2, since the first term corresponds to k=0.
Calculate Binomial Coefficient: Calculate the binomial coefficient for the 3rd term.Using the formula for the binomial coefficient, we have C(6,2)=2!∗(6−2)!6!=(2∗1∗4∗3∗2∗1)(6∗5∗4∗3∗2∗1)=(2∗1)(6∗5)=15.
Write Out 3rd Term: Write out the 3rd term using the binomial coefficient and the variables.The 3rd term is given by C(6,2)⋅(3x)6−2⋅y2=15⋅(3x)4⋅y2.
Simplify 3rd Term: Simplify the 3rd term.Simplify (3x)4 to get 34×x4=81×x4.Then, the 3rd term is 15×81×x4×y2=1215×x4×y2.
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