Q. Find the 6th term in the expansion of (x+2y)8 in simplest form.Answer:
Use Binomial Theorem: To find the 6th term in the expansion of (x+2y)8, we will use the binomial theorem. The binomial theorem states that the nth term in the expansion of (a+b)m is given by the formula C(m,k)⋅am−k⋅bk, where C(m,k) is the binomial coefficient "m choose k". For the 6th term, k will be (x+2y)80 because the first term corresponds to (x+2y)81.
Calculate Binomial Coefficient: First, we need to calculate the binomial coefficient C(8,5). This is equal to 5!×(8−5)!8!, which simplifies to 5!×3!8!.
Calculate Factorials: Calculating the factorial values, we get 8!=8×7×6×5!, 5!=5×4×3×2×1, and 3!=3×2×1. Substituting these into the binomial coefficient formula, we have C(8,5)=3×2×18×7×6.
Calculate Binomial Coefficient: Simplifying the fraction, we get C(8,5)=3×28×7×6=56.
Calculate Remaining Term: Now we need to calculate the rest of the term, which is x(8−5)×(2y)5. This simplifies to x3×(2y)5.
Calculate Power of 2y: Raising 2y to the 5th power gives us 25×y5, which is 32×y5.
Multiply Coefficients: Multiplying the binomial coefficient by the powers of x and y, we get the 6th term: 56×x3×32×y5.
Calculate Final Term: Finally, we multiply 56 by 32 to get the coefficient of the 6th term. This gives us 56×32=1792.
Final Simplified Term: The 6th term in the expansion of (x+2y)8 in simplest form is therefore 1792×x3×y5.
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