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Suatu model sistem persamaan diferensial untuk model kecukupan vaksinasi suatu wabah adalah

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$\\begin{cases} \\dfrac{dN}{dt} &= 2(1-p)N+2(1-p)V-N \\\\ \\dfrac{dV}{dt} &= 2pV+2pN-3V \\end{cases}$

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dengan $N$ menyatakan banyaknya orang yang belum divaksin, $V$ menyatakan banyaknya orang yang divaksin, serta $p$ adalah fraksi populasi yang telah divaksin.

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Perhatikan bahwa titik kesetimbangan model ini adalah di $(0,0)$. Tentukan nilai $p$ terkecil agar titik kesetimbangan ini bersifat stabil. Tuliskan nilainya dalam bentuk pecahan paling sederhana.

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Catatan: Nilai $p$ ini disebut juga dengan nilai kritis, yaitu nilai yang dibutuhkan agar wabah dapat mereda.

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Petunjuk: Karena $p$ menyatakan fraksi, maka $p\\in[0,1]$.

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Misal $\\mathbf{x}(t)=\\begin{bmatrix} N(t) \\\\ V(t) \\end{bmatrix}$. Dengan menggunakan $p=\\dfrac{15}{16}$, jika diberikan nilai awal $N(0)=\\var{k}$ dan $V(0)=0$, maka solusi khusus dari sistem persamaan diferensial tersebut adalah $\\mathbf{x}(t)=\\begin{bmatrix} c_1e^{\\lambda_1t}+c_2e^{\\lambda_2t} \\\\ c_3e^{\\lambda_1t}+ c_4e^{\\lambda_2t} \\end{bmatrix}$.

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Maka $c_1+c_2+c_3+c_4=\\ldots$.

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Mengacu pada solusi (b), $\\displaystyle \\lim\\limits_{t\\to\\infty}\\dfrac{V(t)}{N(t)} = \\ldots$.

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