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Find the 2 nd term in the expansion of 
(3x-4y)^(4) in simplest form.
Answer:

Find the 22 nd term in the expansion of (3x4y)4 (3 x-4 y)^{4} in simplest form.\newlineAnswer:

Full solution

Q. Find the 22 nd term in the expansion of (3x4y)4 (3 x-4 y)^{4} in simplest form.\newlineAnswer:
  1. Apply Binomial Theorem: To find the second term in the expansion of (3x4y)4(3x-4y)^{4}, we will use the binomial theorem. The binomial theorem states that (a+b)n(a+b)^{n} expands to a series of terms that involve powers of aa and bb, with coefficients determined by the binomial coefficients. The general term in the expansion is given by the formula: T(k+1)=(nk)a(nk)bkT(k+1) = \binom{n}{k} \cdot a^{(n-k)} \cdot b^{k}, where (nk)\binom{n}{k} is the binomial coefficient, aa and bb are the terms in the binomial, nn is the power, and kk is the term number minus one.
  2. Calculate Binomial Coefficient: We are looking for the second term, which means k=1k=1. The binomial coefficient for the second term when n=4n=4 and k=1k=1 is 4C14C1, which is equal to 44. This is because 4C1=4!1!(41)!=41=44C1 = \frac{4!}{1! * (4-1)!} = \frac{4}{1} = 4.
  3. Use Formula for Second Term: Now we will plug in the values into the formula for the second term: T(2)=4C1(3x)41(4y)1T(2) = 4C1 \cdot (3x)^{4-1} \cdot (-4y)^1. This simplifies to T(2)=4(3x)3(4y)T(2) = 4 \cdot (3x)^3 \cdot (-4y).
  4. Calculate (3x)3(3x)^3 and (4y)(-4y): Next, we calculate (3x)3(3x)^3 and (4y)(-4y). (3x)3=33×x3=27x3(3x)^3 = 3^3 \times x^3 = 27x^3, and (4y)(-4y) is simply 4y-4y.
  5. Multiply Terms to Find Second Term: Multiplying these together with the binomial coefficient we found earlier, we get T(2)=4×27x3×(4y)=4×108x3×y=432x3yT(2) = 4 \times 27x^3 \times (-4y) = 4 \times -108x^3 \times y = -432x^3y.

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