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Show that the points (1, –1), (5, 2) and (9, 5) are collinear. |
Answer» Let P(1, –1), Q(5, 2) and R(9, 5) be the given points. Then PQ = \(\sqrt{(5-1)^2+(2+1)^2}\) = \(\sqrt{16+9}\) = \(\sqrt{25}\) = 5 QR = \(\sqrt{(9-5)^2+(5-2)^2}\) = \(\sqrt{16+9}\) = \(\sqrt{25}\) = 5 PR = \(\sqrt{(9-1)^2+(5+1)^2}\) = \(\sqrt{64+36}\) = \(\sqrt{100}\) = 10 ⇒ PQ + QR = PR ⇒ P, Q, R are collinear points. |
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