Need help in C4 vectors

[T.Q]

The line l1 has vector equation

r = 8i + 12j + 14k + t(i + j – k),

where t is a parameter.

The point A has coordinates (4, 8, a), where a is a constant. The point B has coordinates
(b, 13, 13), where b is a constant. Points A and B lie on the line l1.

(a) Find the values of a and b.
(3)

Given that the point O is the origin, and that the point P lies on l1 such that OP is
perpendicular to l1,

(b) find the coordinates of P.
(5)


i need help in part B  with explanation plz

[Amr Fouad]

Sorry Cant help ya

I am still doing my A-Ls this year..

Maybe Astar or nid can 

[T.Q]

Sorry Cant help ya

I am still doing my A-Ls this year..

Maybe Astar or nid can 

no problem

i will wait for them

[nid404]

Can u post your answers for the first part...

[T.Q]

Can u post your answers for the first part...

a=18

b=9

[nid404]

I need to know how u got it....
I can't help otherwise...if i get this i can help using my iit books
Cuz evn im doing AS

[Amr Fouad]

I need to know how u got it....
I can't help otherwise...if i get this i can help using my iit books
Cuz evn im doing AS

if ur doing AS, then i guess u can do nth in this q. 

[nid404]

if ur doing AS, then i guess u can do nth in this q. 

I'm doing iit as well...that's engineering entrance stuff...
so if he can tell how he derived the ans to the first part...i maybe able to do some good..hopefully

[T.Q]

I need to know how u got it....
I can't help otherwise...if i get this i can help using my iit books
Cuz evn im doing AS

to find a

4=8+t
t= -4

a=14-t
a=18


to find b

13=12+t
t= 1

b=8+t
b=9

[T.Q]

I'm doing iit as well...that's engineering entrance stuff...
so if he can tell how he derived the ans to the first part...i maybe able to do some good..hopefully

its okay nid

i will wait for astar

[astarmathsandphysics]

Here

[astarmathsandphysics]

The line l1 has vector equation

r = 8i + 12j + 14k + t(i + j – k),

where t is a parameter.

The point A has coordinates (4, 8, a), where a is a constant. The point B has coordinates
(b, 13, 13), where b is a constant. Points A and B lie on the line l1.

(a) Find the values of a and b.
(3)

Given that the point O is the origin, and that the point P lies on l1 such that OP is
perpendicular to l1,

(b) find the coordinates of P.
(5)


i need help in part B  with explanation plz
a)to find a  8i + 12j + 14k + t(i + j – k) =4i+8j+ak
equate the i's to get 8+t=4 so t=-4
equate the j's to get 12+t=8 so again t=-4
equate the k's to get 14-t=14--4=18=a
To find b 8i + 12j + 14k + t(i + j – k) =bi+13j+13k
equate the i's to get 8+t=b (1)
equate the j's to get 12+t=13 so t=1
equate the k's to get14-1=13 so t=1
then from (1) b=9
The tangent vector of the line is (1,1,-1)=v
OP.v=0 since they are perpendicular
OP=8i + 12j + 14k + t(i + j – k)=(8+t)i+(12+t)j+(14-1)k
OP.v=8+t+12+t-(14-t)=6+3t=0 t=-2 then P=8i + 12j + 14k -2(i + j – k)=6i+10j+16k

[T.Q]

The line l1 has vector equation

r = 8i + 12j + 14k + t(i + j – k),

where t is a parameter.

The point A has coordinates (4, 8, a), where a is a constant. The point B has coordinates
(b, 13, 13), where b is a constant. Points A and B lie on the line l1.

(a) Find the values of a and b.
(3)

Given that the point O is the origin, and that the point P lies on l1 such that OP is
perpendicular to l1,

(b) find the coordinates of P.
(5)


i need help in part B  with explanation plz
a)to find a  8i + 12j + 14k + t(i + j – k) =4i+8j+ak
equate the i's to get 8+t=4 so t=-4
equate the j's to get 12+t=8 so again t=-4
equate the k's to get 14-t=14--4=18=a
To find b 8i + 12j + 14k + t(i + j – k) =bi+13j+13k
equate the i's to get 8+t=b (1)
equate the j's to get 12+t=13 so t=1
equate the k's to get14-1=13 so t=1
then from (1) b=9
The tangent vector of the line is (1,1,-1)=v
OP.v=0 since they are perpendicular
OP=8i + 12j + 14k + t(i + j – k)=(8+t)i+(12+t)j+(14-1)k
OP.v=8+t+12+t-(14-t)=6+3t=0 t=-2 then P=8i + 12j + 14k -2(i + j – k)=6i+10j+16k

thanx astar 

+rep