# Thread: Find (alpha), (beta), and (gamma) s.t Vector D = (alpha)VA + (beta)VB + (gamma)VC

1. ## Find (alpha), (beta), and (gamma) s.t Vector D = (alpha)VA + (beta)VB + (gamma)VC

I'm working on an exercise, not sure if I am posting in the right place though... first time on this website

Vector A = 3i - 2j + k

Vector B = -2i + 5j + 4k

Vector C = -4i + j + -2k

Vector D = 2i - j + 4k

determine (alpha), (beta), and (gamma) such that Vector D = (alpha)VA + (beta)VB + (gamma)VC

I have no idea where to start on this, is should I be doing scalar projections or something with unit vectors? Have I missed something obvious??
I got really lost and none of my answers came out right (I know the solution, just not how to get to it)

2. Originally Posted by ania1224
I'm working on an exercise, not sure if I am posting in the right place though... first time on this website

Vector A = 3i - 2j + k

Vector B = -2i + 5j + 4k

Vector C = -4i + j + -2k

Vector D = 2i - j + 4k

determine (alpha), (beta), and (gamma) such that Vector D = (alpha)VA + (beta)VB + (gamma)VC

I have no idea where to start on this, is should I be doing scalar projections or something with unit vectors? Have I missed something obvious??
I got really lost and none of my answers came out right (I know the solution, just not how to get to it)
What are those?

3. ## clarification

Vector A = VA

Vector B = VB

Vector C = VC

4. ## they are

Originally Posted by Subhotosh Khan
What are those?
they are Vector A, Vector B, and Vector C

5. You should review the text book: What is a vector? What are i, j, k? How do we add vectors? How do we multiply a vector by a number?

6. Originally Posted by ania1224
I'm working on an exercise, not sure if I am posting in the right place though... first time on this website

Vector A = 3i - 2j + k

Vector B = -2i + 5j + 4k

Vector C = -4i + j + -2k

Vector D = 2i - j + 4k

determine (alpha), (beta), and (gamma) such that Vector D = (alpha)VA + (beta)VB + (gamma)VC

I have no idea where to start on this, is should I be doing scalar projections or something with unit vectors? Have I missed something obvious??
I got really lost and none of my answers came out right (I know the solution, just not how to get to it)
What would you get for:

(Vector A) + (Vector B) + (Vector C) = ?

Originally Posted by Subhotosh Khan
What would you get for:

(Vector A) + (Vector B) + (Vector C) = ?
Adding them together gets me -3i + 4j + 3k, but I'm not sure how that helps me decide how much to multiply each vector so that they equal Vector D