Q. Find the 6 th term in the expansion of (4x−1)7 in simplest form.Answer:
Use Binomial Theorem: To find the 6th term in the expansion of (4x−1)7, we will use the binomial theorem. The general term in the expansion of (a+b)n is given by T(k+1)=(kn)⋅an−k⋅bk, where (kn) is the binomial coefficient "n choose k". For the 6th term, k=5, since we start counting from k=0 for the first term.
Calculate Binomial Coefficient: First, we calculate the binomial coefficient for n=7 and k=5, which is 7C5. This can be calculated as 5!×(7−5)!7!.
Find 7C5: Calculating 7C5, we get 5!⋅2!7!=2⋅17⋅6=21.
Calculate 6th Term: Now, we will use the binomial coefficient to find the 6th term. The 6th term is T(6)=(57)⋅(4x)7−5⋅(−1)5.
Substitute Values: Substitute the values into the formula to get T(6)=21×(4x)2×(−1)5.
Simplify Term: Simplify the term: T(6)=21×16x2×(−1).
Final Result: Multiplying the numbers together, we get T(6)=−336x2.
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