이차함수 그래프의 꼭짓점 찾기

문제

이차함수 $y = -x^2 + 4x - 1$의 그래프의 꼭짓점의 좌표가 $(p, q)$일 때, $p+q$의 값은?

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<text x="55" y="235" font-family="'Noto Sans KR', sans-serif" font-size="14" fill="#1F2937" text-anchor="middle">O</text>

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<!-- y=1 -->
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<text x="55" y="190" font-family="'Noto Sans KR', sans-serif" font-size="12" fill="#1F2937" text-anchor="end">1</text>
<!-- y=2 -->
<line x1="65" y1="150" x2="75" y2="150" stroke="#1F2937" stroke-width="1" />
<text x="55" y="155" font-family="'Noto Sans KR', sans-serif" font-size="12" fill="#1F2937" text-anchor="end">2</text>
<!-- y=3 -->
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<text x="145" y="105" font-family="'Noto Sans KR', sans-serif" font-size="14" fill="#1F2937" text-anchor="start">(p, q)</text>
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<text x="145" y="125" font-family="'Noto Sans KR', sans-serif" font-size="12" fill="#1F2937" text-anchor="start">(2, 3)</text>

<!-- Equation Label -->
<text x="250" y="180" font-family="'Noto Sans KR', sans-serif" font-size="14" fill="#1F2937" text-anchor="start">y = -x² + 4x - 1</text>