Date | May 2013 | Marks available | 2 | Reference code | 13M.2.sl.TZ1.3 |
Level | SL only | Paper | 2 | Time zone | TZ1 |
Command term | Find | Question number | 3 | Adapted from | N/A |
Question
In the expansion of (3x−2)12(3x−2)12 , the term in x5x5 can be expressed as (12r)×(3x)p×(−2)q(12r)×(3x)p×(−2)q .
(a) Write down the value of pp , of qq and of rr .
(b) Find the coefficient of the term in x5x5 .
Write down the value of pp , of qq and of rr .
Find the coefficient of the term in x5x5 .
Markscheme
(a) p=5p=5 , q=7q=7 , r=7r=7 (accept r=5r=5) A1A1A1 N3
[3 marks]
(b) correct working (A1)
eg (127)×(3x)5×(−2)7(127)×(3x)5×(−2)7 , 792792 , 243243 , −27−27 , 2463436824634368
coefficient of term in x5x5 is −24634368−24634368 A1 N2
Note: Do not award the final A1 for an answer that contains xx.
[2 marks]
Total [5 marks]
p=5p=5 , q=7q=7 , r=7r=7 (accept r=5r=5) A1A1A1 N3
[3 marks]
correct working (A1)
eg (127)×(3x)5×(−2)7(127)×(3x)5×(−2)7 , 792792 , 243243 , −27−27 , 2463436824634368
coefficient of term in x5x5 is −24634368−24634368 A1 N2
Note: Do not award the final A1 for an answer that contains xx.
[2 marks]
Total [5 marks]
Examiners report
Candidates frequently made reasonable attempts at both parts of the question. Those who correctly stated the values in (a) were generally successful in part (b). Many candidates offered the whole term rather than the coefficient in part (b) and lost the final mark. Some candidates appeared to have misread the order of the variables, stating that p=7p=7 (instead of r=7r=7 ), q=5q=5 (instead of p=5p=5) and r=5r=5 or 77 (instead of q=5q=5 or 77). A large number of candidates did not make the connection between parts (a) and (b).
Candidates frequently made reasonable attempts at both parts of the question. Those who correctly stated the values in (a) were generally successful in part (b). Many candidates offered the whole term rather than the coefficient in part (b) and lost the final mark. Some candidates appeared to have misread the order of the variables, stating that p=7p=7 (instead of r=7r=7 ), q=5q=5 (instead of p=5p=5) and r=5r=5 or 77 (instead of q=5q=5 or 77). A large number of candidates did not make the connection between parts (a) and (b).
Candidates frequently made reasonable attempts at both parts of the question. Those who correctly stated the values in (a) were generally successful in part (b). Many candidates offered the whole term rather than the coefficient in part (b) and lost the final mark. Some candidates appeared to have misread the order of the variables, stating that p=7p=7 (instead of r=7r=7 ), q=5q=5 (instead of p=5p=5) and r=5r=5 or 77 (instead of q=5q=5 or 77). A large number of candidates did not make the connection between parts (a) and (b).