Posted by Kim K on .
Consider the following three vectors: a = 3i + 4j ; b = pi + 2j ; c = mi + nj , where
m, n and p are constants. If:
a + b = 9i + 6j
a.c = 10
b x c = 2k
Show that p = 6, and determine values for m and n.
i got the p=6
as for the rest...what i did so far
b x c = 2k
so (6i x nj) + 2j x mi
6nk + 2mk = 2k...cancel out k's and simplify by dividing through by 2
so
3n + 1m = 1
___
a.c = 10
so
3i.mi + 4j.nj = 10
3m + 4n = 10
i would say solve simulatneously...but
when i do that, the answer doesn't come out to
m = 2 and n = 1
instead, i get m=3.2 and n=1.4

Phys... vectors 
bobpursley,
On the cross product.
ixj=k but jxi=k. I think you missed the minus
The equation on the dot is correct. 
Phys... vectors 
Kim K,
wow...lol...look at what one little mistake can do
THANKS!~ i got it now