the binomial expansion - solutions

Upload: wolfretonmaths

Post on 10-Oct-2015

30 views

Category:

Documents


0 download

TRANSCRIPT

  • AQA Core 2 Sequences and series

    1 of 2 15/01/13 MEI

    Section 4: The binomial expansion Solutions to Exercise

    1. Pascals triangle: 1

    1 1

    1 2 1

    1 3 3 1

    1 4 6 4 1

    1 5 10 10 5 1

    1 6 15 20 15 6 1

    (i) 6 6 5 4 3 2( 1) 6 15 20 15 6 1x x x x x x x

    (ii) 5 5 4 1 3 2 2 3 4 5

    5 4 3 2

    5 4 3 2

    ( 2) 5 ( 2) 10 ( 2) 10 ( 2) 5 ( 2) ( 2)

    5 2 10 4 10 8 5 16 32

    10 40 80 80 32

    x x x x x x

    x x x x x

    x x x x x

    (iii) 4 4 3 2

    4 3 2

    4 3 2

    (2 1) (2 ) 4(2 ) 6(2 ) 4(2 ) 1

    16 4 8 6 4 8 1

    16 32 24 8 1

    x x x x x

    x x x x

    x x x x

    (iv) 3 3 2 2 3

    2 3

    2 3

    (2 3 ) 2 3(2) ( 3 ) 3(2)( 3 ) ( 3 )

    8 3 4 3 3 2 9 27

    8 33 54 27

    x x x x

    x x x

    x x x

    2. (i) 8 8 7 6

    3

    1 2 38 7 56

    (ii) 9 9 9 8

    5 4

    27 6

    1 2 3 49 2 7 126

    (iii) 12 12

    4

    11 10 59

    1 2

    3 411 9 5 495

    (iv) 20 20 20

    18 2

    1019

    1 2

    10 19 190

    3. (i) Term in x4

    4 4 415 15 14 13 12(2 ) 16 21840

    4 1 2 3 4x x x

    Coefficient of x4 is 21840

  • AQA C2 Series 4 Exercise solutions

    2 of 2 15/01/13 MEI

    (ii) Term in x23 2 23 25 2 232

    23 23

    25(3) ( ) (3) ( )

    23

    25 249 2700

    1 2

    x C x

    x x

    Coefficient of x23 is -2700.

    (iii) Term in x 4 6

    6 2

    4

    10 10 9 8 71210

    4 1 2 3 4

    xx xx x

    Coefficient of x2 is 210.

    4. 4 2(1 ) 1 4 6 ...x x x 7 2(1 ) 1 7 21 ...x x x

    4 7 2 2

    2 2

    2 2 2

    2

    (1 ) (1 ) 1 4 6 ... 1 7 21 ...

    (1 7 21 ) 4 (1 7 ) 6 ...

    1 7 21 4 28 6 ...

    1 3 ...

    x x x x x x

    x x x x x

    x x x x x

    x x

    5. (i) 15 2 215 14

    (1 ) 1 15 ... 1 15 105 ...1 2

    x x x x x

    (ii) Putting x = 0.01: 15 2

    15

    (1 0.01) 1 15 0.01 105 0.01 ...

    0.99 1 0.15 0.0105 ... 0.8605

    (iii) Percentage error 15

    15

    0.8605 0.99100 0.051%

    0.99

    6. (i) 9 2 3

    9 2 3212 2

    9 8 9 8 71 1 9 ...2 2 1 2 2 1 2 3 2

    1 9 ...

    x x x x

    x x x

    (ii) Putting x = 0.1: 9

    9 2 3212 2

    9

    0.11 1 0.1 9 0.1 0.1 ...2

    1.05 1 0.45 0.09 0.0105 ... 1.5505

    (iii) Percentage error 9

    9

    1.5505 1.05100 0.053%

    1.05