Vector addition

[Sjein]

Please check my calculations.
a)AD=AF+FE+ED
FE=FA+AB+BE=b+a-3b=a-2b
AD=-b+a-2b+a=2a-3b

b)EA=EF+FA=-(a-2b)+b=-a+2b+b=3b-a

c)FC=FE+ED+DC=a-2b+a+2b=2a

I got stuck when I noticed that my solution for FC does not include vector b. Is it okay with the task?

 

[pka]

I agree with your answers.

 

[Sjein]

I agree with your answers.

What about my last question?

 

[pka]

$\bf{\vec{b}+\vec{a}-3\vec{b}+\vec{a}+2\vec{b}=2\vec{a}}$

 

[Sjein]

I

$\bf{\vec{b}+\vec{a}-3\vec{b}+\vec{a}+2\vec{b}=2\vec{a}}$

But is it okay that there is no vector b in the answer?

 

[pka]

But is it okay that there is no vector b in the answer?

Surely you see that $\bf\vec{b}-3\vec{b}+2\vec{b}=\vec{0}~???$

 

[Sjein]

Surely you see that $\bf\vec{b}-3\vec{b}+2\vec{b}=\vec{0}~???$

The task is to express FC in terms of vectors a and b, not in terms of vectors a and b or a, b

 

[pka]

The task is to express FC in terms of vectors a and b, not in terms of vectors a and b or a, b

O.K. Then $\bf{\vec{b}+\vec{a}-3\vec{b}+\vec{a}+2\vec{b}=2\vec{a}}+0\vec{b}$

 

[Sjein]

[MATH][/MATH]

O.K. Then $\bf{\vec{b}+\vec{a}-3\vec{b}+\vec{a}+2\vec{b}=2\vec{a}}+0\vec{b}$

Thanks. Now I can follow your thoughts

 

[Steven G]

You want vector b, you got it! 2a=2a+0b

Can you explain why there is no vector b? That is more important then just asking if your answer is ok