Transcription of Math 110: Worksheet 1 Solutions
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Math 110: Worksheet 1 SolutionsAugust 30 Thursday Aug. 241. Determine whether or not the following sets form vector spaces over the given fields.(a) The setVof all matrices of the form(1ab1)wherea, b R, overRwith standardaddition and scalar thatVis not closed under addition: fora, b, c, d R, we have(1ab1)and(1cd1)but(1ab1)+(1cd1)=(2a+ cb+d2)/ conclude thatVis not a vector space with the given operations.(b) The setVof all matrices of the form(1ab1)wherea, b R, overRwith addition and scalar multiplication defined by(1ab1) (1cd1)=(1a+cb+d1), k (1ab1)=(1kakb1).We claim thatVis indeed a vector space with the given operations. Note firstthatVis closed under the addtion and scalar multiplication operations: for(1ab1),(1cd1) Vandk R, we have(1ab1) (1cd1)=(1a+cb+d1) Vandk (1ab1)=(1kakb1) 1:Observe that(1ab1) (1cd1)=(1a+cb+d1)( defn. of addition)=(1c+ad+b1)( comm. of addition inR)=(1cd1) (1ab1)( addition)VS 2:Note that((1ab1) (1cd1)) (1ef1)=(1a+cb+d1) (1ef1)( defn.)
2. By de nition, every eld F has a multiplicative identity, an element e such that ex = x for every element x 2F. What is the multiplicative identity for R? Prove that the multiplicative identity is unique for any given eld. The multiplicative identity for R is the number 1 as 1 x = x for all x 2R.
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