I Can someone help me with this problem?

  • Thread starter princiebebe57
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In summary, the resultant vector of combining 2A - 3B, where A = 4i + 3j and B = 9i + 8j, is equal to -19i - 18j and has a magnitude of approximately 26.172. The formula for the length of a vector is the square root of the sum of the squares of its components, which can be thought of as the Pythagorean theorem.
  • #1
princiebebe57
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0
What is the length of the resultant vector of combining 2A - 3B where vector A= 4i + 3j and vector B= 9i + 8j?
 
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  • #2
First thing is to multiply the vectors by the given amounts... post your result.
 
  • #3
is it -19i + 30j?
 
  • #4
princiebebe57 said:
is it -19i + 30j?
No, what's 2A and 3B?
 
  • #5
2A = 8i + 6j
3B = 27i + 24j

is that correct?
 
  • #6
princiebebe57 said:
2A = 8i + 6j
3B = 27i + 24j

is that correct?
Yep -- now do the subtraction.
 
  • #7
so (8i + 6j)-(27i + 24j)?
 
  • #8
princiebebe57 said:
so (8i + 6j)-(27i + 24j)?
Yeah. What's it equal?
 
  • #9
is it -19i - 18j?
 
  • #10
princiebebe57 said:
is it -19i - 18j?
Yeah -- and the length (magnitude) is...
 
  • #11
i'm stuck at that!
 
  • #12
princiebebe57 said:
i'm stuck at that!

The magnitude of a vector [itex]x\vec{i}+y\vec{j}=\sqrt{x^2+y^2}[/itex]. So, what does give you in your case?
 
Last edited:
  • #13
so is it 26.172?
 
  • #14
princiebebe57 said:
so is it 26.172?
Yep -- to 3 decimal places.
 
  • #15
Thank you so much!
 
  • #16
Hello princiebebe57,

you may find this website here interesting. It contains some questions and answers on vectors.
If you want to remember the formula for the length of a vector, it helps thinking of the Pythagorean theorem.
 

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