1
The coefficient of x2 in the expansion of 2x +1 by 3 whole square

1 +6 x + 12 x 2 + 8x 3

Explanation:

We must use our knowledge of the binomial expansion:

Method 1:

We can use:

(

x

+

1

)

n

=

1

+

n

x

+

n

(

n

−

1

)

2

!

x

2

+

n

(

n

−

1

)

(

n

−

2

)

3

!

x

3

+

...

Substituting  

n

=

3

and  

x

for  

2

x

⇒

(

2

x

+

1

)

3

=

1

+

(

3

⋅

2

x

)

+

3

⋅

2

2

!

⋅

(

2

x

)

2

+

3

⋅

2

⋅

1

3

!

⋅

(

2

x

)

3

=

1

+

6

x

+

12

x

2

+

8

x

3

Method 2:

We can use:

(

A

+

B

)

n

=

A

n

+

(

n

1

)

A

n

−

1

B

1

+

(

n

2

)

A

n

−

2

B

2

+

...

Letting  

A

=

2

x

and

B

=

1

for this circumstance:

(

2

x

+

1

)

3

=

(

2

x

)

3

+

(

3

1

)

(

2

x

)

2

(

1

)

+

(

3

2

)

(

2

x

)

1

(

1

)

2

+

(

3

3

)

(

2

x

)

0

(

1

)

3

=

8

x

3

+

12

x

2

+

6

x

+

1

Step-by-step explanation:

pentagon

step-by-step explanation:

the coordinates   a(5, -2), b(3,-1),c(-4,-4) d(-3,8) and e(-1,4) forms the vertices of the polygon when they are connected in order.

in order to classify that which polygon is it with the given coordinates, first count the number of vertices and then count the number of sides it can make with these vertices.

since, the given coordinates have five vertices, therefore, it will make five sides. moreover, pentagon is regular in nature therefore it will be convex.

now, a polygon with five sides is known as pentagon, therefore, the given polygon is the pentagon.

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this