$$$\left(x - 2\right)^{5}$$$을 전개
사용자 입력
$$$\left(x - 2\right)^{5}$$$을(를) 전개하세요.
풀이
전개는 다음 공식으로 주어진다: $$$\left(a + b\right)^{n} = \sum_{k=0}^{n} {\binom{n}{k}} a^{n - k} b^{k}$$$, 여기서 $$${\binom{n}{k}} = \frac{n!}{\left(n - k\right)! k!}$$$ 및 $$$n! = 1 \cdot 2 \cdot \ldots \cdot n$$$.
다음이 성립한다: $$$a = x$$$, $$$b = -2$$$, 및 $$$n = 5$$$.
따라서 $$$\left(x - 2\right)^{5} = \sum_{k=0}^{5} {\binom{5}{k}} x^{5 - k} \left(-2\right)^{k}$$$.
이제 $$$0$$$부터 $$$5$$$까지의 모든 $$$k$$$ 값에 대해 곱을 계산하세요.
$$$k = 0$$$: $$${\binom{5}{0}} x^{5 - 0} \left(-2\right)^{0} = \frac{5!}{\left(5 - 0\right)! 0!} x^{5 - 0} \left(-2\right)^{0} = x^{5}$$$
$$$k = 1$$$: $$${\binom{5}{1}} x^{5 - 1} \left(-2\right)^{1} = \frac{5!}{\left(5 - 1\right)! 1!} x^{5 - 1} \left(-2\right)^{1} = - 10 x^{4}$$$
$$$k = 2$$$: $$${\binom{5}{2}} x^{5 - 2} \left(-2\right)^{2} = \frac{5!}{\left(5 - 2\right)! 2!} x^{5 - 2} \left(-2\right)^{2} = 40 x^{3}$$$
$$$k = 3$$$: $$${\binom{5}{3}} x^{5 - 3} \left(-2\right)^{3} = \frac{5!}{\left(5 - 3\right)! 3!} x^{5 - 3} \left(-2\right)^{3} = - 80 x^{2}$$$
$$$k = 4$$$: $$${\binom{5}{4}} x^{5 - 4} \left(-2\right)^{4} = \frac{5!}{\left(5 - 4\right)! 4!} x^{5 - 4} \left(-2\right)^{4} = 80 x$$$
$$$k = 5$$$: $$${\binom{5}{5}} x^{5 - 5} \left(-2\right)^{5} = \frac{5!}{\left(5 - 5\right)! 5!} x^{5 - 5} \left(-2\right)^{5} = -32$$$
따라서, $$$\left(x - 2\right)^{5} = x^{5} - 10 x^{4} + 40 x^{3} - 80 x^{2} + 80 x - 32$$$.
정답
$$$\left(x - 2\right)^{5} = x^{5} - 10 x^{4} + 40 x^{3} - 80 x^{2} + 80 x - 32$$$A