Question

coefficient of x^3 in (x^2-2x+1)(x^2+2x+1) is

Answer 1

Step-by-step explanation:

T

r+1

in (2x

2

−

3x

1

)

9

=

9

C

r

(2x

2

)

9−r

(−

3x

1

)

r

=

9

C

r

2

9−r

(−

3

1

)x

18−2r−r

This has got to be multiplied by the terms of the first factor i.e.,1+x+2x

2

=x

0

+x+2x

2

Hence the power of x in (1) after multiplication with the terms of first factor

will be 18−3r,18−3r+1,18−3r+2

Each should be equal to 3

∴18−3r=3⇒r=5

∴18−3r+1=3 ∴r=

3

16

rejected

Answer 2

Step-by-step explanation:

coefficient of x^3 in (x^2-2x+1)(x^2+2x+1) is

=-2+2

=0