Moderate -0.8 This is a straightforward coordinate geometry question requiring students to calculate two or three gradients and verify that two are negative reciprocals (perpendicular). It's a standard C1 exercise with clear method and minimal steps, making it easier than average, though not trivial since it requires correct application of the perpendicularity condition.
5 The vertices of a triangle have coordinates ( 1,5 ), ( $- 3,7$ ) and ( $- 2 , - 1$ ).\\
Show that the triangle is right-angled.
\hfill \mbox{\textit{OCR MEI C1 Q5 [4]}}