Question 852131
1) Find the magnitude of v first.
{{{abs(v)=sqrt((-7)^2+(-2)^2)=sqrt(53)}}}
Find the "u" unit vector by dividing it by its magnitude.
{{{abs(u)=sqrt(6^2+(-2)^2+(-8)^2)=sqrt(104)= 2*sqrt(26)}}}
So the u unit vector would be 
({{{6 /(2*sqrt(26))}}} ,{{{-2/(2*sqrt(26))}}},{{{-8/(2*sqrt(26))}}})
So then multiply the u unit vector by the magnitude of v.
({{{(6*sqrt(53)) /(2*sqrt(26))}}} ,{{{(-2*sqrt(53))/(2*sqrt(26))}}},{{{(-8*sqrt(53))/(2*sqrt(26))}}})
({{{3*sqrt(53/26)}}} ,{{{-sqrt(53/26)}}},{{{-4*sqrt(53/26))}}})
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2) The v unit vector is 
({{{0.0}}} ,{{{-7/sqrt(53)}}},{{{-2/sqrt(53)}}})
Just multiply this by {{{4}}},
({{{0.0}}} ,{{{-28/sqrt(53)}}},{{{-8/sqrt(53)}}})
({{{0.0}}} ,{{{-(28/53)*sqrt(53)}}},{{{-(2/53)*sqrt(53)}}})