Which of the following vectors can be written as a linear combination of the vectors (1, 1, 2), (1, 2, 1) and (2, 1, 5)? (0.4,3.7,-1.5) (0.2,0) None of the selections is correct. All the selections are correct

Respuesta :

Answer with explanation:

Let, A=[1,1,2]

B=[1,2,1]

C=[2,1,5]

⇒Now, Writing vector , A in terms of Linear combination of C and B

A=x B +y C

⇒[1,1,2]=x× [1,2,1] + y×[2,1,5]

1.→1 = x +2 y

2.→ 1=2 x +y

3.→ 2= x+ 5 y

Equation 3 - Equation 1

→3 y=1

[tex]y=\frac{1}{3}[/tex]

[tex]1=x+\frac{2}{3}\\\\x=1 -\frac{2}{3}\\\\x=\frac{1}{3}[/tex]

So, Vector A , can be written as Linear Combination of B and C.

⇒Now, Writing vector , B in terms of Linear combination of A and C

Now, let, B = p A+q C

→[1,2,1]=p× [1,1,2] +q ×[2,1,5]

4.→1= p +2 q

5.→2=p +q

6.→1=2 p +5 q

Equation 5 - Equation 4

-q =1

q= -1

→2= p -1

→p=2+1

→p=3

So, Vector B , can be written as Linear Combination of A and C.

⇒Now, Writing vector , C in terms of Linear combination of A and B

C=m A + n B

[2,1,5] = m×[1,1,2] + n× [1,2,1]

7.→2= m+n

8.→1=m +2 n

9.→5=2 m +  n

Equation 8 - Equation 7

n= -1

→m+ (-1)=2

→m=2+1

→m=3

So, Vector C , can be written as Linear Combination of A and B.

So, All the three vectors , A=[1,1,2],B=[1,2,1],C=[2,1,5] can be written as Linear combination of each other.

⇒≡But , the two vectors, (0.4,3.7,-1.5) (0.2,0),can't be written as Linear combination of each other as first vector is of order, 1×3, and second is of order, 1×2.

None of the selections is correct.

How to apply linear combinations and linear independence to determine the existence of a relationship with a given vector

In this case, we must check the existence of a set of real coefficients such that the following two linear combinations exist:

[tex]\alpha_{1}\cdot (1, 1, 2)+\alpha_{2}\cdot (1, 2,1)+\alpha_{3}\cdot (2, 1, 5) = (0.4, 3.7, -1.5)[/tex]   (1)

[tex]\alpha_{4}\cdot (1,1,2)+\alpha_{5}\cdot (1,2,1) + \alpha_{6}\cdot (2,1,5) = (0, 2, 0)[/tex]   (2)

Now we proceed to solve each linear combination:

First system

[tex]\alpha_{1}+\alpha_{2}+2\cdot \alpha_{3} = 0.4[/tex]

[tex]\alpha_{1}+2\cdot \alpha_{2}+\alpha_{3} = 3.7[/tex]

[tex]2\cdot \alpha_{1}+\alpha_{2}+5\cdot \alpha_{3} = -1.5[/tex]

The system has no solution, since the third equation is a linear combination of the first and second ones.

Second system

[tex]\alpha_{4}+\alpha_{5}+2\cdot \alpha_{6} = 0[/tex]

[tex]\alpha_{4}+2\cdot \alpha_{5}+\alpha_{6} = 2[/tex]

[tex]2\cdot \alpha_{4}+\alpha_{5}+5\cdot \alpha_{6} = 0[/tex]

The system has no solution, since the third equation is a linear combination of the first and second ones.

None of the selections is correct. [tex]\blacksquare[/tex]

To learn more on linear combinations, we kindly invite to check this verified question: https://brainly.com/question/9672435