By definition, two vectors are perpendicular if the value
of their dot product is zero.
u*v = 0
(1)
[(1-m)*i+(1+m)*j]*[(1+2m)*i+4*j] = (1-m)*(1+2m) +
4*(1+m) (2)
We'll equate (1) and
(2):
(1-m)*(1+2m) + 4*(1+m) =
0
We'll remove the brackets:
1
+ 2m - m - 2m^2 + 4 + 4m = 0
We'll combine like
terms:
-2m^2 + 5m + 5 =
0
We'll multiply by -1:
2m^2 -
5m - 5 = 0
We'll apply quadratic
formula:
m1 =
[5+sqrt(25+40)]/4
m1 =
(5+sqrt65)/4
m2 =
(5-sqrt65)/4
The values of the parameter "m",
for the vector u to be perpendicular to the vector v, are: {(5-sqrt65)/4 ;
(5+sqrt65)/4}.
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