Answer: QR = 16
By Apollonius theorem, since PM is a median (QM = MR = \(\tfrac12\)QR),
\(PQ^2 + PR^2 = 2PM^2 + 2QM^2\).
\(290 = 2(9)^2 + 2QM^2 = 162 + 2QM^2\)
∴ \(2QM^2 = 128\), so \(QM^2 = 64\) and QM = 8.
∴ QR = 2 × QM = 2 × 8 = 16.
Best answer
Answer: QR = 16
By Apollonius theorem, since PM is a median (QM = MR = \(\tfrac12\)QR),
\(PQ^2 + PR^2 = 2PM^2 + 2QM^2\).
\(290 = 2(9)^2 + 2QM^2 = 162 + 2QM^2\)
∴ \(2QM^2 = 128\), so \(QM^2 = 64\) and QM = 8.
∴ QR = 2 × QM = 2 × 8 = 16.
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