2.18: Stationary area of a trapezium

0606/21/O/N/16 — Question 7 · 9 marks

2.18 diagram
The diagram shows a trapezium PQRSPQRS in which QRQR is parallel to PSPS, PQ=3 cmPQ = 3\text{ cm}, QR=x cmQR = x\text{ cm}, and PS=(x+14) cmPS = (x + 14)\text{ cm}.
(i)
Show that the area, A cm2A\text{ cm}^{2}, of the trapezium PQRSPQRS is given by A=(7+x)9x2A = (7 + x)\sqrt{9 - x^{2}}.
[2]
(ii)
Given that xx can vary, find the stationary value of AA.
[7]