Question

4. What is the first term?
A. 4x2
D. - 2x2
C. 2x2
B. -4x2
5. Which of the following is the expanded form of (x - 5)2?
A. x2 - 25
B. x2 - 5x - 25 C. x2 - 10x + 25
D. x2 - 10x + 25​

Answer 1

Step-by-step explanation:

Co-efficient of x

5

in (1+x

2

)

5

(1+x)

4

Binomial expansion of

(a+b)

n

=

n

C

a

a

n

+

n

C

1

a

n−1

b

1

+...

n

C

2

a

n−r

b

r

+...

∴(1+x

2

)

5

(1+x)

4

(

5

C

0

(1)+

5

C

1

(1)x

2

+

5

C

2

(1)(x

2

)

2

+

5

C

3

(x

2

)

3

+

5

C

4

(x

2

)

4

+

5

C

c

(x

2

)

5

)

×(

4

C

0

(1)+

4

C

1

(x)+

4

C

2

(x)

2

+

4

C

3

(x)

3

+

4

C

4

(x)

4

)

∴{

5

C

2

x

4

×

4

C

1

x+

5

C

1

x+

5

C

1

(x

2

)×

4

C

3

(x)

3

}

∴ coefficient of x

5

⇒(

2×1

5×4

×4)x

5

+(5×4)x

5

⇒(10×4+20)x

5

⇒60x

5

∴ coefficient of x

5

⇒

60

(option D)