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Show that the following mappings are not linear: (a) \(F: \mathbf{R}^{2} \rightarrow \mathbf{R}^{2}\) defined by \(F(x, y)=(x y, x)\) (b) \(F: \mathbf{R}^{2} \rightarrow \mathbf{R}^{3}\) defined by \(F(x, y)=(x+3,2 y, x+y)\) (c) \(F: \mathbf{R}^{3} \rightarrow \mathbf{R}^{2}\) defined by \(F(x, y, z)=(|x|, y+z)\)

Short Answer

Expert verified
In summary, all three mappings are not linear transformations as they fail to satisfy the properties of addition and/or scalar multiplication. Specifically: (a) Fails the addition property: (x1 + x2)(y1 + y2) ≠ x1 * y1 + x2 * y2 (b) Fails both addition and scalar multiplication properties: x1 + x2 + 3 ≠ x1 + x2 + 6, and c * x + 3 ≠ c * x + 3 * c (c) Fails both addition and scalar multiplication properties: (|x1| + |x2|) ≠ |(x1 + x2)|, and c * |x| ≠ |c * x|

Step by step solution

01

(a) Testing Mapping F for addition and scalar multiplication

: We start by testing the addition property for mapping (a): F(x1 + x2, y1 + y2) = ((x1 + x2)(y1 + y2), (x1 + x2)) To show it is not a linear mapping, we put F(u) + F(v): F(x1, y1) + F(x2, y2) = ((x1 * y1, x1) + (x2 * y2, x2)) = ((x1 * y1 + x2 * y2), (x1 + x2)) If they don't match, we can conclude the mapping is not linear in addition: (x1 + x2)(y1 + y2) ≠ x1 * y1 + x2 * y2 Now, we test for scalar multiplication: F(c * x, c * y) = (c * x * c * y, c * x) To show it is not a linear mapping, we put c * F(u): c * F(x, y) = c * (x * y, x) = (c * x * y, c * x) Comparing these, we see that they match: c * x * c * y = c * x * y As one of the properties (addition) is not satisfied, we can conclude that mapping (a) is not linear.
02

(b) Testing Mapping F for addition and scalar multiplication

: We start by testing the addition property for mapping (b): F(x1 + x2, y1 + y2) = (x1 + x2 + 3, 2 * (y1 + y2), (x1 + x2) + (y1 + y2)) To show it is linear, we put F(u) + F(v): F(x1, y1) + F(x2, y2) = ((x1 + 3, 2 * y1, x1 + y1) + (x2 + 3, 2 * y2, x2 + y2)) = ((x1 + x2 + 6), (2 * (y1 + y2), (x1 + x2) + (y1 + y2)) Comparing these, we see that they don't match: x1 + x2 + 3 ≠ x1 + x2 + 6 Now, we test for scalar multiplication: F(c * x, c * y) = (c * x + 3, 2 * c * y, c * x + c * y) To show it is linear, we put c * F(u): c * F(x, y) = c * (x + 3, 2 * y, x + y) = (c * x + 3 * c, 2 * c * y, c * (x + y)) Comparing these, we see that they don't match: c * x + 3 ≠ c * x + 3 * c As both properties (addition and scalar multiplication) are not satisfied, we can conclude that mapping (b) is not linear.
03

(c) Testing Mapping F for addition and scalar multiplication

: We start by testing the addition property for mapping (c): F(x1 + x2, y1 + y2, z1 + z2) = (|(x1 + x2)|, (y1 + y2) + (z1 + z2)) To show it is linear, we put F(u) + F(v): F(x1, y1, z1) + F(x2, y2, z2) = (|x1|, y1 + z1) + (|x2|, y2 + z2) = (|x1| + |x2|, (y1 + z1) + (y2 + z2)) Comparing these, we see that they don't match: (|x1| + |x2|) ≠ |(x1 + x2)| Now, we test for scalar multiplication: F(c * x, c * y, c * z) = (|c * x|, c * y + c * z) To show it is linear, we put c * F(u): c * F(x, y, z) = c * (|x|, y + z) = (c * |x|, c * (y + z)) Comparing these, we see that they don't match: c * |x| ≠ |c * x| As both properties (addition and scalar multiplication) are not satisfied, we can conclude that mapping (c) is not linear.

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Most popular questions from this chapter

Let \(A\) be an \(n \times n\) matrix. Prove that $$ \operatorname{dim}\left(\operatorname{span}\left(\left\\{I_{n}, A, A^{2}, \ldots\right\\}\right)\right) \leq n . $$

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Find \(F(a, b),\) where the linear map \(F: \mathbf{R}^{2} \rightarrow \mathbf{R}^{2}\) is defined by \(F(1,2)=(3,-1)\) and \(F(0,1)=(2,1).\)

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