SOLUTION: Hello, i have this problem Find a*b a = 2i-j , b = j-3k I've tried this so far: 2i-j*j-3k = 2i-3k-j I feel like this is so wrong. I'd appreciate an explanation on how

Algebra ->  Vectors -> SOLUTION: Hello, i have this problem Find a*b a = 2i-j , b = j-3k I've tried this so far: 2i-j*j-3k = 2i-3k-j I feel like this is so wrong. I'd appreciate an explanation on how       Log On


   

Question 972955: Hello, i have this problem
Find a*b
a = 2i-j , b = j-3k
I've tried this so far: 2i-j*j-3k = 2i-3k-j
I feel like this is so wrong.
I'd appreciate an explanation on how to handle vectors with an "i", "j", "k" etc behind them. Also, what are these called?
Thanks

Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

Find
if a+=+2i-j and b+=+j-3k, then a%2Ab=%282i-j%29%28+j-3k%29
recall the rule for multiplication of binomials:

1. multiply each term in one binomial by each term in the other binomial
2. add those answers together, and simplify if needed

so, you have:
a%2Ab=%282i-j%29%28+j-3k%29
a%2Ab=+2i%2Aj-2i%2A3k-j%2Aj-j%2A%28-3k%29
a%2Ab=+2ij-6ik-j%5E2%2B3jk