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    In M1, i am very confused with how to make vectors equal. For example in this question; Given that a = 2i + j and b=i+3j find x if a + xb is parallel to the vector i. I know that I have to form some sort of simultaneous equation and the answer is -1/3, but I can't work out how to get there? Thanks!
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    (Original post by mayjb)
    In M1, i am very confused with how to make vectors equal. For example in this question; Given that a = 2i + j and b=i+3j find x if a + xb is parallel to the vector i. I know that I have to form some sort of simultaneous equation and the answer is -1/3, but I can't work out how to get there? Thanks!
    Misread.

    Do what RDKGames said
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    (Original post by mayjb)
    In M1, i am very confused with how to make vectors equal. For example in this question; Given that a = 2i + j and b=i+3j find x if a + xb is parallel to the vector i. I know that I have to form some sort of simultaneous equation and the answer is -1/3, but I can't work out how to get there? Thanks!
    For the expression to be parallel to i, the j component must be 0.
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    (Original post by RDKGames)
    For the expression to be parallel to i, the i component must be 0.
    I understand that, but I don't know what you do if it gets more complicated and is equal to say -i-3j?? I just don't understand the method you follow to get to the answer.
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    (Original post by mayjb)
    I understand that, but I don't know what you do if it gets more complicated and is equal to say -i-3j?? I just don't understand the method you follow to get to the answer.
    Then yes, simultaneous equations. You would need 2 scalars for both vectors in order to reach any point/vector in the plane from two vectors which aren't parallel to each other, so that's where the two variables come from.
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    (Original post by mayjb)
    I understand that, but I don't know what you do if it gets more complicated and is equal to say -i-3j?? I just don't understand the method you follow to get to the answer.
    Do you understand that if vectors  \mathbf{a} and  \mathbf{b} are parallel then  \mathbf{a}=k\mathbf{b} (scalar constant k), if so it's not too hard to see that a vector parallel to the x axis the vector must be of the form   k\begin{pmatrix} 1 \\ 0 \end{pmatrix} .
 
 
 
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