FINAL TUTORIAL
MTH3201 LINEAR ALGEBRA
1. Linear combination or not
(a) 𝛵: ℛ 3 → ℛ 2 ; 𝛵 𝑥, 𝑦, 𝑧 = (𝑥 − 𝑦, 𝑦 − 𝑧)
                       Condition given, please follow

  𝐿𝑒𝑡 𝑢 = 𝑥1 , 𝑦1 , 𝑧1 𝑎𝑛𝑑 𝑣 = 𝑥2 , 𝑦2 , 𝑧2
 (i) 𝑢 + 𝑣 = 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 , 𝑧1 + 𝑧2
     𝛵 𝑢 + 𝑣 = 𝛵 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 , 𝑧1 + 𝑧2
    By follow the condition,
                = 𝑥1 + 𝑥2 − 𝑦1 − 𝑦2 , 𝑦1 + 𝑦2 − 𝑧1 − 𝑧2
                = 𝑥1 − 𝑦1 + 𝑥2 − 𝑦2 , 𝑦1 − 𝑧1 + 𝑦2 − 𝑧2
                = 𝑥1 − 𝑦1 , 𝑦1 − 𝑧1 ) + (𝑥2 − 𝑦2 , 𝑦2 − 𝑧2
                = 𝛵(𝑢) + 𝛵(𝑣)
 (ii) 𝐼𝑓 𝑘 𝑖𝑠 𝑎𝑛𝑦 𝑠𝑐𝑎𝑙𝑎𝑟, 𝑘 ∈ ℜ,
       𝑘𝑢 = 𝑘𝑥1 , 𝑘𝑦1 , 𝑘𝑧1                           𝑆𝑖𝑛𝑐𝑒 𝛵 𝑢 + 𝑣 = 𝛵 𝑢 + 𝛵 𝑣 ,
        𝛵 (𝑘𝑢) = 𝛵 𝑘𝑥1 , 𝑘𝑦1 , 𝑘𝑧1                   ∴ 𝛵 is linear combination
               = 𝑘𝑥1 − 𝑘𝑦1 , 𝑘𝑦1 − 𝑘𝑧1
               = 𝑘 𝑥1 − 𝑦1 , 𝑦1 − 𝑧1
               = 𝑘𝛵(𝑢 )
1. Linear combination or not
                                   𝑥          𝑦
(d) 𝛵: ℛ 2 → ℛ; 𝛵 𝑥, 𝑦 =                             𝐿𝑒𝑡 𝑢 = 𝑥1 , 𝑦1 𝑎𝑛𝑑 𝑣 = 𝑥2 , 𝑦2
                                  𝑥+ 𝑦       𝑥− 𝑦
                    Condition given, please follow

(i) 𝑢 + 𝑣 = 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 ,    𝛵 𝑢 + 𝑣 = 𝛵 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2
                                          𝑥 + 𝑥                 𝑦1 + 𝑦2
By follow the condition,
                         𝛵 𝑢 + 𝑣 = 𝑥 + 𝑥1 + 𝑦2 + 𝑦         𝑥1 + 𝑥2 − 𝑦1 − 𝑦2
                                      1    2    1      2
= 𝑥1 + 𝑥2 𝑥1 + 𝑥2 − 𝑦1 − 𝑦2 − 𝑦1 + 𝑦2 𝑥1 + 𝑥2 + 𝑦1 + 𝑦2
= 𝑥1 2 + 𝑥1 𝑥2 − 𝑥1 𝑦1 − 𝑥1 𝑦2 + 𝑥1 𝑥2 + 𝑥2 2 − 𝑥2 𝑦1 − 𝑥2 𝑦2
                               − 𝑦1 𝑥1 + 𝑦1 𝑥2 + 𝑦1 2 + 𝑦1 𝑦2 + 𝑦2 𝑥1 + 𝑦2 𝑥2 + 𝑦2 𝑦1 + 𝑦2 2
= 𝑥1 2 + 𝑥2 2 − 𝑦1 2 − 𝑦2 2 + 2𝑥1 𝑥2 − 2𝑦1 𝑥2 − 2𝑥1 𝑦1 − 2𝑥1 𝑦2 − 2𝑥2 𝑦1 − 2𝑥2 𝑦2
∗∗ 𝑒𝑞𝑢𝑎𝑙 𝑡𝑜 𝛵 𝑢 + 𝛵 𝑣 ? ? ?
  𝛵 𝑢 + 𝛵 𝑣 = 𝛵 𝑥1 , 𝑦1 + 𝛵 𝑥2 , 𝑦2                                compare
                 𝑥1         𝑦1         𝑥2               𝑦2
            = 𝑥 + 𝑦      𝑥1 − 𝑦1  + 𝑥 + 𝑦            𝑥2 − 𝑦2
               1      1              2    2
               = 𝑥1 2 + 𝑥2 2 − 𝑦1 2 − 𝑦2 2 − 2𝑥1 𝑦1 − 2𝑥2 𝑦2
 𝑆𝑖𝑛𝑐𝑒 𝛵 𝑢 + 𝑣 ≠ 𝛵 𝑢 + 𝛵 𝑣 , ∴ 𝛵 is not linear combination
2(a)   𝛵2 ∙ 𝛵1     𝑝 𝑥    = 𝛵2 𝛵1 (𝑝 𝑥 )    𝐶𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑔𝑖𝑣𝑒𝑛: 𝛵1 𝑝(𝑥) = 𝑝 𝑥 − 1 ,
                          = 𝛵2 𝑝(𝑥 − 1)             𝛵2 𝑝 𝑥 = 𝑝 𝑥 + 2

                          = 𝑝(𝑥 − 1 + 2)
                          = 𝑝(𝑥 + 1)

 (b)     𝛵1 ∙ 𝛵2    𝑝 𝑥    = 𝛵1 𝛵2 (𝑝 𝑥 )
                           = 𝛵1 𝑝(𝑥 + 2)
                           = 𝑝(𝑥 + 2 − 1)
                           = 𝑝(𝑥 + 1)
3(a)             𝑎   𝑏             𝑎   𝑏          𝑎   𝑐
       𝛵1 ∙ 𝛵2           = 𝛵1 𝛵2           = 𝛵1           = 𝑎 − 𝑐 + 4𝑏 − 𝑑
                 𝑐   𝑑             𝑐   𝑑          𝑏   𝑑

                        𝑎 𝑏
   𝐶𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑔𝑖𝑣𝑒𝑛: 𝛵1       = 𝑎 − 𝑏 + 4𝑐 − 𝑑,
                        𝑐 𝑑
                    𝑎 𝑏     𝑎 𝑐
               𝛵2         =
                    𝑐 𝑑     𝑏 𝑑


              𝑎 𝑏                𝑎 𝑏
 (b)   𝛵2 ∙ 𝛵1        = 𝛵2 𝛵1            = 𝛵2 (𝑎 − 𝑏 + 4𝑐 − 𝑑)
              𝑐 𝑑                𝑐 𝑑
       ∴ 𝑑𝑜𝑒𝑠 𝑛𝑜𝑡 𝑒𝑥𝑖𝑠𝑡, 𝑖𝑚𝑎𝑔𝑒 𝑇1 𝑛𝑜𝑡 𝑠𝑢𝑏𝑗𝑒𝑐𝑡 𝑜𝑓 𝑑𝑜𝑚𝑎𝑖𝑛 𝑇2
4(a)                                          𝑥2 𝑝 𝑥 = 𝑥2 + 𝑥
                                (i)               𝑝 𝑥 = 1 + 1/𝑥
                                             𝑝 𝑥 is not in domain of 𝑝2
                                             ∴ x 2 +x is not in range(T)
  𝛵 𝑝 𝑥    = 𝑥 2 𝑝(𝑥)
                                      (ii)

                                                             𝑥2 𝑝 𝑥 = 𝑥 + 1
                        (iii)                                 𝑝 𝑥 = 1/𝑥 + 1/𝑥 2
                                                            𝑝 𝑥 is not in domain of 𝑝2
                                                            ∴ x + 1 is not in range(T)


   𝑥2 𝑝 𝑥 = 3 − 𝑥2
              3
     𝑝 𝑥 = 2−1
              𝑥
𝑝 𝑥 is not in domain of 𝑝2
∴ 3 − x 2 is not in range(T)
4(b)                                             𝛵 𝑥 2 = 𝑥 2 ∙ 𝑥 2= 𝑥 4
                               (i)                      𝑥4 ≠ 0
                                                 ∴not in Kernel(T)

 𝛵 𝑝 𝑥   = 𝑥 2 𝑝(𝑥)
                                     (ii)

                                                      𝛵 0 = 𝑥2 ∙ 0 = 0
                       (iii)                          ∴ in Kernel(T)



                       𝛵 𝑥 + 1 = 𝑥2 𝑥 + 1 = 𝑥3 + 𝑥2 ≠ 0
                      ∴not in Kernel(T)
5(a)    𝐴𝑥 = 0
                             𝑟1 /4
    4 5        7 0        3𝑟1 + 2𝑟2      1 5/4 7/4 0             13𝑟2 − 17𝑟3 1   5/4  7/4 0
   −6 1        −1 0                      0 17 19 0                           0    1  19/17 0
                            𝑟2 + 3𝑟3                               𝑟2 /17
    3 6        4 0                       0 13   7 0                          0    0   128 0
                                              19
   𝑟3 /128        1 0     6/17 0         𝑟2 −    𝑟       1   0    0 0
                                              17 3
                  0 1     19/17 0                        0   1    0 0
       5                                       6
𝑟1 −     𝑟        0 0       1   0        𝑟1 −    𝑟       0   0    1 0
       4 2                                    17 3
             ∴ Since 𝑥1 = 0, 𝑥2 = 0, 𝑥3 = 0. There is no basis for Kernel (T)

                                     4   5    7
             ∴ Basis for image (T)= −6 , 1 , −1
                                     3   6    4
5(b)   𝐴𝑥 = 0
   1   −1 3 0          5𝑟1 − 𝑟2     1 −1   3 0           𝑟2 − 𝑟3    1 −1  3    0
   5    6 −4 0                      0 −11 19 0                      0 1 −19/11 0
   7    4    2 0       7𝑟1 − 𝑟3     0 −11 19 0            𝑟2 /-11   0 0   0    0
                                                         19           14
   𝑟1 + 𝑟2     1   0 14/11 0         𝐿𝑒𝑡 𝑥3 = 𝑡 , 𝑥2 =      𝑡, 𝑥1 = −    𝑡
                                                         11           11
               0   1 −19/11 0
                            0                 14
               0   0   0                    −      𝑡
                                              11        𝑡 −14
                                        𝑥 = 19       =     19
                                                 𝑡     11
                                             11            11
                                               𝑡
                                     1 −1
             ∴ Basis for range (T)= 5 , 6
                                     7    4
                                     −14
             ∴ Basis for kernel (T)= 19
                                      11
6. 𝑇 𝑥, 𝑦, 𝑧 = (0,0,0)                                           2𝑥 + 4𝑦 − 6𝑧 = 0
  (2𝑥 + 4𝑦 − 6𝑧, 𝑥 − 2𝑦 + 𝑧, 5𝑥 − 2𝑦 − 3𝑧) = (0,0,0)                𝑥 − 2𝑦 + 𝑧 = 0
                                                                 5𝑥 − 2𝑦 − 3𝑧 = 0
                            𝑟1 /2
   2    4      −6 0       𝑟1 − 𝑟2    1      2    −3 0       𝑟3 + 𝑟2      1   2   −3 0
   1   −2      1 0                   0      8    −8 0                    0   1   −1 0
                        5𝑟2 − 𝑟3                              𝑟2 /8      0   0    0 0
   5   −2      −3 0                  0     −8     8 0

   𝑟2 − 2𝑟2       1 0    −1 0            𝐿𝑒𝑡 𝑥3 = 𝑡 ,   𝑥2 = 𝑡, 𝑥1 = 𝑡
                  0 1    −1 0
                                            𝑡     1
                  0 0     0 0
                                         𝑥= 𝑡 = 𝑡 1
                                             𝑡    1


                                      2   4
              ∴ Basis for range (T)= 1 , −2
                                      5 −2
                                      1
              ∴ Basis for kernel (T)= 1
                                      1
TAMAT

Tutorial 9 mth 3201

  • 2.
  • 3.
    1. Linear combinationor not (a) 𝛵: ℛ 3 → ℛ 2 ; 𝛵 𝑥, 𝑦, 𝑧 = (𝑥 − 𝑦, 𝑦 − 𝑧) Condition given, please follow 𝐿𝑒𝑡 𝑢 = 𝑥1 , 𝑦1 , 𝑧1 𝑎𝑛𝑑 𝑣 = 𝑥2 , 𝑦2 , 𝑧2 (i) 𝑢 + 𝑣 = 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 , 𝑧1 + 𝑧2 𝛵 𝑢 + 𝑣 = 𝛵 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 , 𝑧1 + 𝑧2 By follow the condition, = 𝑥1 + 𝑥2 − 𝑦1 − 𝑦2 , 𝑦1 + 𝑦2 − 𝑧1 − 𝑧2 = 𝑥1 − 𝑦1 + 𝑥2 − 𝑦2 , 𝑦1 − 𝑧1 + 𝑦2 − 𝑧2 = 𝑥1 − 𝑦1 , 𝑦1 − 𝑧1 ) + (𝑥2 − 𝑦2 , 𝑦2 − 𝑧2 = 𝛵(𝑢) + 𝛵(𝑣) (ii) 𝐼𝑓 𝑘 𝑖𝑠 𝑎𝑛𝑦 𝑠𝑐𝑎𝑙𝑎𝑟, 𝑘 ∈ ℜ, 𝑘𝑢 = 𝑘𝑥1 , 𝑘𝑦1 , 𝑘𝑧1 𝑆𝑖𝑛𝑐𝑒 𝛵 𝑢 + 𝑣 = 𝛵 𝑢 + 𝛵 𝑣 , 𝛵 (𝑘𝑢) = 𝛵 𝑘𝑥1 , 𝑘𝑦1 , 𝑘𝑧1 ∴ 𝛵 is linear combination = 𝑘𝑥1 − 𝑘𝑦1 , 𝑘𝑦1 − 𝑘𝑧1 = 𝑘 𝑥1 − 𝑦1 , 𝑦1 − 𝑧1 = 𝑘𝛵(𝑢 )
  • 4.
    1. Linear combinationor not 𝑥 𝑦 (d) 𝛵: ℛ 2 → ℛ; 𝛵 𝑥, 𝑦 = 𝐿𝑒𝑡 𝑢 = 𝑥1 , 𝑦1 𝑎𝑛𝑑 𝑣 = 𝑥2 , 𝑦2 𝑥+ 𝑦 𝑥− 𝑦 Condition given, please follow (i) 𝑢 + 𝑣 = 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 , 𝛵 𝑢 + 𝑣 = 𝛵 𝑥1 + 𝑥2 , 𝑦1 + 𝑦2 𝑥 + 𝑥 𝑦1 + 𝑦2 By follow the condition, 𝛵 𝑢 + 𝑣 = 𝑥 + 𝑥1 + 𝑦2 + 𝑦 𝑥1 + 𝑥2 − 𝑦1 − 𝑦2 1 2 1 2 = 𝑥1 + 𝑥2 𝑥1 + 𝑥2 − 𝑦1 − 𝑦2 − 𝑦1 + 𝑦2 𝑥1 + 𝑥2 + 𝑦1 + 𝑦2 = 𝑥1 2 + 𝑥1 𝑥2 − 𝑥1 𝑦1 − 𝑥1 𝑦2 + 𝑥1 𝑥2 + 𝑥2 2 − 𝑥2 𝑦1 − 𝑥2 𝑦2 − 𝑦1 𝑥1 + 𝑦1 𝑥2 + 𝑦1 2 + 𝑦1 𝑦2 + 𝑦2 𝑥1 + 𝑦2 𝑥2 + 𝑦2 𝑦1 + 𝑦2 2 = 𝑥1 2 + 𝑥2 2 − 𝑦1 2 − 𝑦2 2 + 2𝑥1 𝑥2 − 2𝑦1 𝑥2 − 2𝑥1 𝑦1 − 2𝑥1 𝑦2 − 2𝑥2 𝑦1 − 2𝑥2 𝑦2 ∗∗ 𝑒𝑞𝑢𝑎𝑙 𝑡𝑜 𝛵 𝑢 + 𝛵 𝑣 ? ? ? 𝛵 𝑢 + 𝛵 𝑣 = 𝛵 𝑥1 , 𝑦1 + 𝛵 𝑥2 , 𝑦2 compare 𝑥1 𝑦1 𝑥2 𝑦2 = 𝑥 + 𝑦 𝑥1 − 𝑦1 + 𝑥 + 𝑦 𝑥2 − 𝑦2 1 1 2 2 = 𝑥1 2 + 𝑥2 2 − 𝑦1 2 − 𝑦2 2 − 2𝑥1 𝑦1 − 2𝑥2 𝑦2 𝑆𝑖𝑛𝑐𝑒 𝛵 𝑢 + 𝑣 ≠ 𝛵 𝑢 + 𝛵 𝑣 , ∴ 𝛵 is not linear combination
  • 5.
    2(a) 𝛵2 ∙ 𝛵1 𝑝 𝑥 = 𝛵2 𝛵1 (𝑝 𝑥 ) 𝐶𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑔𝑖𝑣𝑒𝑛: 𝛵1 𝑝(𝑥) = 𝑝 𝑥 − 1 , = 𝛵2 𝑝(𝑥 − 1) 𝛵2 𝑝 𝑥 = 𝑝 𝑥 + 2 = 𝑝(𝑥 − 1 + 2) = 𝑝(𝑥 + 1) (b) 𝛵1 ∙ 𝛵2 𝑝 𝑥 = 𝛵1 𝛵2 (𝑝 𝑥 ) = 𝛵1 𝑝(𝑥 + 2) = 𝑝(𝑥 + 2 − 1) = 𝑝(𝑥 + 1)
  • 6.
    3(a) 𝑎 𝑏 𝑎 𝑏 𝑎 𝑐 𝛵1 ∙ 𝛵2 = 𝛵1 𝛵2 = 𝛵1 = 𝑎 − 𝑐 + 4𝑏 − 𝑑 𝑐 𝑑 𝑐 𝑑 𝑏 𝑑 𝑎 𝑏 𝐶𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑔𝑖𝑣𝑒𝑛: 𝛵1 = 𝑎 − 𝑏 + 4𝑐 − 𝑑, 𝑐 𝑑 𝑎 𝑏 𝑎 𝑐 𝛵2 = 𝑐 𝑑 𝑏 𝑑 𝑎 𝑏 𝑎 𝑏 (b) 𝛵2 ∙ 𝛵1 = 𝛵2 𝛵1 = 𝛵2 (𝑎 − 𝑏 + 4𝑐 − 𝑑) 𝑐 𝑑 𝑐 𝑑 ∴ 𝑑𝑜𝑒𝑠 𝑛𝑜𝑡 𝑒𝑥𝑖𝑠𝑡, 𝑖𝑚𝑎𝑔𝑒 𝑇1 𝑛𝑜𝑡 𝑠𝑢𝑏𝑗𝑒𝑐𝑡 𝑜𝑓 𝑑𝑜𝑚𝑎𝑖𝑛 𝑇2
  • 7.
    4(a) 𝑥2 𝑝 𝑥 = 𝑥2 + 𝑥 (i) 𝑝 𝑥 = 1 + 1/𝑥 𝑝 𝑥 is not in domain of 𝑝2 ∴ x 2 +x is not in range(T) 𝛵 𝑝 𝑥 = 𝑥 2 𝑝(𝑥) (ii) 𝑥2 𝑝 𝑥 = 𝑥 + 1 (iii) 𝑝 𝑥 = 1/𝑥 + 1/𝑥 2 𝑝 𝑥 is not in domain of 𝑝2 ∴ x + 1 is not in range(T) 𝑥2 𝑝 𝑥 = 3 − 𝑥2 3 𝑝 𝑥 = 2−1 𝑥 𝑝 𝑥 is not in domain of 𝑝2 ∴ 3 − x 2 is not in range(T)
  • 8.
    4(b) 𝛵 𝑥 2 = 𝑥 2 ∙ 𝑥 2= 𝑥 4 (i) 𝑥4 ≠ 0 ∴not in Kernel(T) 𝛵 𝑝 𝑥 = 𝑥 2 𝑝(𝑥) (ii) 𝛵 0 = 𝑥2 ∙ 0 = 0 (iii) ∴ in Kernel(T) 𝛵 𝑥 + 1 = 𝑥2 𝑥 + 1 = 𝑥3 + 𝑥2 ≠ 0 ∴not in Kernel(T)
  • 9.
    5(a) 𝐴𝑥 = 0 𝑟1 /4 4 5 7 0 3𝑟1 + 2𝑟2 1 5/4 7/4 0 13𝑟2 − 17𝑟3 1 5/4 7/4 0 −6 1 −1 0 0 17 19 0 0 1 19/17 0 𝑟2 + 3𝑟3 𝑟2 /17 3 6 4 0 0 13 7 0 0 0 128 0 19 𝑟3 /128 1 0 6/17 0 𝑟2 − 𝑟 1 0 0 0 17 3 0 1 19/17 0 0 1 0 0 5 6 𝑟1 − 𝑟 0 0 1 0 𝑟1 − 𝑟 0 0 1 0 4 2 17 3 ∴ Since 𝑥1 = 0, 𝑥2 = 0, 𝑥3 = 0. There is no basis for Kernel (T) 4 5 7 ∴ Basis for image (T)= −6 , 1 , −1 3 6 4
  • 10.
    5(b) 𝐴𝑥 = 0 1 −1 3 0 5𝑟1 − 𝑟2 1 −1 3 0 𝑟2 − 𝑟3 1 −1 3 0 5 6 −4 0 0 −11 19 0 0 1 −19/11 0 7 4 2 0 7𝑟1 − 𝑟3 0 −11 19 0 𝑟2 /-11 0 0 0 0 19 14 𝑟1 + 𝑟2 1 0 14/11 0 𝐿𝑒𝑡 𝑥3 = 𝑡 , 𝑥2 = 𝑡, 𝑥1 = − 𝑡 11 11 0 1 −19/11 0 0 14 0 0 0 − 𝑡 11 𝑡 −14 𝑥 = 19 = 19 𝑡 11 11 11 𝑡 1 −1 ∴ Basis for range (T)= 5 , 6 7 4 −14 ∴ Basis for kernel (T)= 19 11
  • 11.
    6. 𝑇 𝑥,𝑦, 𝑧 = (0,0,0) 2𝑥 + 4𝑦 − 6𝑧 = 0 (2𝑥 + 4𝑦 − 6𝑧, 𝑥 − 2𝑦 + 𝑧, 5𝑥 − 2𝑦 − 3𝑧) = (0,0,0) 𝑥 − 2𝑦 + 𝑧 = 0 5𝑥 − 2𝑦 − 3𝑧 = 0 𝑟1 /2 2 4 −6 0 𝑟1 − 𝑟2 1 2 −3 0 𝑟3 + 𝑟2 1 2 −3 0 1 −2 1 0 0 8 −8 0 0 1 −1 0 5𝑟2 − 𝑟3 𝑟2 /8 0 0 0 0 5 −2 −3 0 0 −8 8 0 𝑟2 − 2𝑟2 1 0 −1 0 𝐿𝑒𝑡 𝑥3 = 𝑡 , 𝑥2 = 𝑡, 𝑥1 = 𝑡 0 1 −1 0 𝑡 1 0 0 0 0 𝑥= 𝑡 = 𝑡 1 𝑡 1 2 4 ∴ Basis for range (T)= 1 , −2 5 −2 1 ∴ Basis for kernel (T)= 1 1
  • 12.