The line 3x + 4y = 15 cuts the curve 2xy = 9 at the points A and B. Find the length of the line AB.

Mark scheme

Marking points from the official mark scheme (May/June 2013). The mark or mark type is shown in brackets.

1. [1] M1 for attempt to obtain equ in one variable
2. [1] DM1 for attempt to solve a 3 term quadratic in that variable
3. [1] A1 for each 'pair', x values must be simplified to single integer form
4. [1] A1 for each 'pair', x values must be simplified to single integer form
5. [1] M1 for a correct attempt to find AB, must have non zero differences and be using points calculated previously.
6. [1] AB = 1.25 A1