Murray Flynn
07/02/2023 · Primary School
Diketahui vektor \( \bar{a}=\left(\begin{array}{c}k+5 \\ k^{3} \\ k^{2}\end{array}\right) \) dan \( \bar{b}=\left(\begin{array}{c}-1 \\ -1 \\ 3\end{array}\right) \). Jika \( \bar{a} \) dan \( \bar{b} \) tegak lurus, nilai \( k=\ldots \) \( \begin{array}{ll}\text { A. } 4 & \text { D. }-1 \\ \text { B. } 3 & \text { E. }-5\end{array} \)
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Step-by-step Solution
Untuk menentukan nilai \( k \) ketika vektor \( \bar{a} \) dan \( \bar{b} \) tegak lurus, kita dapat menggunakan konsep bahwa jika dua vektor tegak lurus, maka produk skalar mereka adalah nol.
Diberikan vektor \( \bar{a}=\left(\begin{array}{c}k+5 \\ k^{3} \\ k^{2}\end{array}\right) \) dan \( \bar{b}=\left(\begin{array}{c}-1 \\ -1 \\ 3\end{array}\right) \).
Kita dapat menentukan produk skalar antara \( \bar{a} \) dan \( \bar{b} \) sebagai berikut:
\[ \bar{a} \cdot \bar{b} = (k+5)(-1) + (k^{3})(-1) + (k^{2})(3) \]
Untuk \( \bar{a} \) dan \( \bar{b} \) tegak lurus, maka \( \bar{a} \cdot \bar{b} = 0 \). Maka kita dapat menulis:
\[ (k+5)(-1) + (k^{3})(-1) + (k^{2})(3) = 0 \]
Sekarang, kita dapat memecahkan persamaan ini untuk menemukan nilai \( k \).
Solve the equation by following steps:
- step0: Solve for \(k\):
\(\left(k+5\right)\left(-1\right)+k^{3}\left(-1\right)+k^{2}\times 3=0\)
- step1: Simplify:
\(-k-5-k^{3}+3k^{2}=0\)
- step2: Factor the expression:
\(\left(-1-k\right)\left(5+k^{2}-4k\right)=0\)
- step3: Separate into possible cases:
\(\begin{align}&-1-k=0\\&5+k^{2}-4k=0\end{align}\)
- step4: Solve the equation:
\(\begin{align}&k=-1\\&k \notin \mathbb{R}\end{align}\)
- step5: Find the union:
\(k=-1\)
Nilai \( k \) ketika vektor \( \bar{a} \) dan \( \bar{b} \) tegak lurus adalah \( k = -1 \). Jadi, jawaban yang benar adalah \( k = -1 \) atau pilihan jawaban D.
Quick Answer
Nilai \( k \) adalah \( -1 \). Jawaban yang benar adalah D.
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