1.

If `A-B={:[(18,1,-9),(11,12,2)]:}andA+3B={:[(26,1,3),(-13,-16,10)]:}`, then find A.A. `{:[(20,1,6),(5,5,4)]:}`B. `{:[(20,1,6),(-5,-5,4)]:}`C. `{:[(20,1,-6),(5,5,4)]:}`D. `{:[(20,1,-6),(-5,-5,-4)]:}`

Answer» Correct Answer - C
`A-B={:[(18,1,-9),(11,12,2)]:}` (1)
`A+3B={:[(26,1,3),(-13,-16,10)]:}` (2)
`3xx(1)rArr3A-3B={:[(54,3,-27),(33,36,6)]:}` (3)
Add Eqs. (2) and (3), we get
A=3B+3A-3B
`={:[(26,1,3),(-13,-16,10)]:}+{:[(54,3,-27),(33,36,6)]:}`
`4A={:[(80,4,-24),(20,20,16)]:}`
`A{:[(20,1,-6),(5,5,4)]:}`.


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