Q. Find the 4 th term in the expansion of (x+2y)6 in simplest form.Answer:
Apply Binomial Theorem: To find the 4th term in the expansion of (x+2y)6, 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 4th term, k will be (x+2y)60 because the first term corresponds to (x+2y)61.
Calculate Binomial Coefficient: We calculate the binomial coefficient for the 4th term, which is C(6,3). This is equal to 3!×(6−3)!6!, where “!“ denotes factorial.
Simplify Factorials: Calculating the factorials, we get 6!=6×5×4×3×2×1, 3!=3×2×1, and (6−3)!=3!=3×2×1. Substituting these into the binomial coefficient formula, we have C(6,3)=3×2×16×5×4.
Calculate Binomial Coefficient: Simplifying the binomial coefficient, we get C(6,3)=3×2×16×5×4=20.
Calculate Powers: Now we need to calculate the rest of the term, which is x(6−3)×(2y)3. This simplifies to x3×(2y)3.
Simplify Powers: Calculating the powers, we get x3×(2y)3=x3×8y3, since (2y)3=23×y3=8y3.
Multiply Coefficients and Powers: Multiplying the binomial coefficient by the calculated powers, we get the 4th term: 20×x3×8y3.
Simplify Final Term: Simplifying the expression, we get the 4th term in simplest form: 160x3y3.
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