simple vector

[5x-7y]2+[5y-7z]2+[5z-7x]2

the maximum value of the above expression

where[] denotes modulus and x y z are unit vectors

i am sorry for confusing u all i have edited it once again

25 Answers

11
Subash ·

mod(x+y+z)2>=0

3+2(x.y+y.z+z.x)>=0

2(x.y+y.z+z.x)>=-3

E=given expression=25+49-2.35(x.y+y.z+z.x)

<=25+49+35.3

<=179

3
msp ·

tx dude

11
Subash ·

see thefirst three lines for the proof

3
msp ·

it shud be 109 and also the minimum value for the exp (x.y+y.z+z.x) shud be -1 not -3

3
msp ·

ya mistaked

11
Subash ·

not exactly i+j+k≠0 even though the three points form vertices of a triangle

3
msp ·

am i rite or rong please reply

1
mkagenius ·

yup!

11
Subash ·

exacty mate u were rite

1
mkagenius ·

mod(x+y+z)2>=0

3+2(x.y+y.z+z.x)>=0

2(x.y+y.z+z.x)>=-3

E=given expression=3*(25+49)-2.35(x.y+y.z+z.x)

<=3*(25+49)+35*3

<=327

3
msp ·

any three vectors can be made to be the vertices of a triangle

and so the x+y+z=0

1
mkagenius ·

take all the vectors at 120 degrees u may get the correct answer which i think is 327.

11
Subash ·

guyz check this one out

this was the solution available to me

i know the answer is wrong

11
Subash ·

ne one trying

21
tapanmast Vora ·

i'm gettin 292....
subhash plz chk da ans its gotta be wrong...

take x= i
y =i
z = -i

u'll get 292.........

1
mkagenius ·

it sud atleast b more than 222,
i m getting 327.

1
mkagenius ·

it sud atleast b more than 222,
i m getting 327.

11
Subash ·

why shud x+y+z be zero

3
msp ·

i think this hint really helps u

x+y+z=0

and mod(x)=mod(y)=mod(z)=1

and simplify the given expression

use x=a1i+a2j+a3k

similarly for other two vectors.

i think i was correct with my method.

can anyone post if i was wrong...

11
Subash ·

the answer given is 179 but ihave got doubts can some one post ur solutions

11
virang1 Jhaveri ·

The solution is 24* 3 = 72

Pls tell me if the ans is right?

1
aatmanvora ·

is da ans as big as 74*3+70???

11
Subash ·

x,y,z are unit vectors i have edited the question but 12 is not the correct answer

3
msp ·

i am getting 12 and i assumed x,y,z are unit vectors

21
tapanmast Vora ·

thinkinggg......

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