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What is the constant term in the expansion of the binomial [tex]$(x-2)^4$[/tex]?

A. -16
B. 16
C. -32
D. 32

Sagot :

To determine the constant term in the expansion of the binomial [tex]\((x-2)^4\)[/tex], we can use the Binomial Theorem. The Binomial Theorem states:

[tex]\[ (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \][/tex]

In this case, [tex]\(a = x\)[/tex], [tex]\(b = -2\)[/tex], and [tex]\(n = 4\)[/tex]. The expansion of [tex]\((x-2)^4\)[/tex] can be written as:

[tex]\[ (x-2)^4 = \sum_{k=0}^{4} \binom{4}{k} x^{4-k} (-2)^k \][/tex]

We are specifically interested in the constant term in the expansion. The constant term is the term where there is no [tex]\(x\)[/tex] present, meaning [tex]\(x\)[/tex] must be raised to the power of 0. For this to happen, we need [tex]\(4-k = 0\)[/tex], that is, [tex]\(k = 4\)[/tex].

With [tex]\(k = 4\)[/tex], the constant term is:

[tex]\[ \binom{4}{4} x^{4-4} (-2)^4 \][/tex]

Simplifying each part, we have:

[tex]\[ \binom{4}{4} = 1 \][/tex]

[tex]\[ x^0 = 1 \][/tex]

[tex]\[ (-2)^4 = 16 \][/tex]

Therefore, the constant term is:

[tex]\[ 1 \cdot 1 \cdot 16 = 16 \][/tex]

So, the constant term in the expansion of [tex]\((x-2)^4\)[/tex] is:

[tex]\[ \boxed{16} \][/tex]

Hence, the correct answer is B. 16.