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Homework Help: Proof of sums of linear transformations

  1. Jan 28, 2010 #1
    Given linear transformations S: Rn --> Rm and T: Rn --> Rm, show the following:
    a) S+T is a linear transformation
    b) cS is a linear transformation

    I know that since both S and T are linear transformations on their own, they satisfy the properties for being a linear transformation, which is that for some transformation T, T(x+y)=T(x) + T(y), and T(cx)=cT(x). So I tried doing the same sort of procedure for the sum of the transformations, so that (S+T)(x)=S(x) + T(x) and S(cx)=cS(x). This just doesn't seem like a very intricate way of proving the sums of linear transformations is a linear transformation and that a scalar multiplied by a linear transformation is a linear transformation.

    Any help is greatly appreciated!
    Last edited: Jan 28, 2010
  2. jcsd
  3. Jan 28, 2010 #2


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    Homework Helper

    Why not? You defined (S+T)(x) = S(x) + T(x). Now you only need to check if S+T is a linear transformation, i.e. that for all x, y and [tex]\alpha[/tex], [tex]\beta[/tex] , (S+T)([tex]\alpha[/tex]x+[tex]\beta[/tex]y)=[tex]\alpha[/tex](S+T)(x) + [tex]\beta[/tex](S+T)(y) holds.
  4. Jan 28, 2010 #3


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    Science Advisor

    There is no requirement that proofs be "intricate"!
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