Q. Find the 2 nd term in the expansion of (3x−4y)4 in simplest form.Answer:
Apply Binomial Theorem: To find the second term in the expansion of (3x−4y)4, we will use the binomial theorem. The binomial theorem states that (a+b)n expands to a series of terms that involve powers of a and b, with coefficients determined by the binomial coefficients. The general term in the expansion is given by the formula: T(k+1)=(kn)⋅a(n−k)⋅bk, where (kn) is the binomial coefficient, a and b are the terms in the binomial, n is the power, and k is the term number minus one.
Calculate Binomial Coefficient: We are looking for the second term, which means k=1. The binomial coefficient for the second term when n=4 and k=1 is 4C1, which is equal to 4. This is because 4C1=1!∗(4−1)!4!=14=4.
Use Formula for Second Term: Now we will plug in the values into the formula for the second term: T(2)=4C1⋅(3x)4−1⋅(−4y)1. This simplifies to T(2)=4⋅(3x)3⋅(−4y).
Calculate (3x)3 and (−4y): Next, we calculate (3x)3 and (−4y). (3x)3=33×x3=27x3, and (−4y) is simply −4y.
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=−432x3y.
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