# why addition?and how to do c?

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#1
Anyone know what's wrong with my answer in c? And why in a the vectors should undergo addition instead of subtraction?
Last edited by Hedwigeeeee; 8 months ago
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8 months ago
#2
(Original post by Wuxinyu)
Anyone know what's wrong with my answer in c? And why in a the vectors should undergo addition instead of subtraction?
In "a" the vectors are subtracted. It's just that

In "c".

You can subtract the position of the motor boat at time t from the position of s at time t and solve for when it's equal to 0. This is what you look to have tried to do, HOWEVER the position of the motor boat is simply t(pi+qj). Both positions are relative to the "origin", O. There is no need to add (-4i-2j) to the motor boat's position.
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#3
(Original post by ghostwalker)
In "a" the vectors are subtracted. It's just that

In "c".

You can subtract the position of the motor boat at time t from the position of s at time t and solve for when it's equal to 0. This is what you look to have tried to do, HOWEVER the position of the motor boat is simply t(pi+qj). Both positions are relative to the "origin", O. There is no need to add (-4i-2j) to the motor boat's position.
ok， thank u
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