Linear Algebra

84 Chapter Two. Vector SpacesLinear systems won’t go away. But from now on our primary objects of studywill be vector spaces.Exercises1.17 Name the zero vector for each of these vector spaces.(a) The space of degree three polynomials under the natural operations.(b) The space of 2×4 matrices.(c) The space {f: [0..1] → R ∣ ∣ f is continuous}.(d) The space of real-valued functions of one natural number variable.̌ 1.18 Find the additive inverse, in the vector space, of the vector.(a) In P 3 , the vector −3 − 2x + x 2 .(b) In the space 2×2,( ) 1 −1.0 3(c) In {ae x + be −x ∣ ∣ a, b ∈ R}, the space of functions of the real variable x underthe natural operations, the vector 3e x − 2e −x .̌ 1.19 For each, list three elements and then show it is a vector space.(a) The set of linear polynomials P 1 = {a 0 + a 1 x ∣ ∣ a0 , a 1 ∈ R} under the usualpolynomial addition and scalar multiplication operations.(b) The set of linear polynomials {a 0 + a 1 x ∣ ∣ a0 − 2a 1 = 0}, under the usual polynomialaddition and scalar multiplication operations.Hint. Use Example 1.3 as a guide. Most of the ten conditions are just verifications.1.20 For each, list three elements and then show it is a vector space.(a) The set of 2×2 matrices with real entries under the usual matrix operations.(b) The set of 2×2 matrices with real entries where the 2, 1 entry is zero, underthe usual matrix operations.̌ 1.21 For each, list three elements and then show it is a vector space.(a) The set of three-component row vectors with their usual operations.(b) The set⎛ ⎞x{ ⎜y⎟⎝ z ⎠ ∈ ∣ R4 x + y − z + w = 0}wunder the operations inherited from R 4 .̌ 1.22 Show that each of these is not a vector space. (Hint. Check closure by listingtwo members of each set and trying some operations on them.)(a) Under the operations inherited from R 3 , this set⎛ ⎞x{ ⎝y⎠ ∈ R ∣ 3 x + y + z = 1}z(b) Under the operations inherited from R 3 , this set⎛ ⎞x{ ⎝y⎠ ∈ R ∣ 3 x 2 + y 2 + z 2 = 1}z(c) Under the usual matrix operations,( ) a 1 ∣∣{ a, b, c ∈ R}b c