1.

Let `A=" diag "[3,-5,7]" and "B=" diag "[-1,2,4].` ltbr. Find (i) (A+B) (ii) (A-B) (iii) -5A (iv) (2A+3B).`

Answer» We have
`A=[{:(3,0,0),(0,-5,0),(0,0,7):}]" and "B=[{:(-1,0,0),(0,2,0),(0,0,4):}].`
`:." "(i)A+B=[{:(3,0,0),(0,-5,0),(0,0,7):}]+[{:(-1,0,0),(0,2,0),(0,0,4):}]=[{:(2," "0,0),(0,-3,0),(0," "0,11):}].`
(ii) `(A-B)=A+(-B)`
`=[{:(3,0,0),(0,-5,0),(0,0,7):}]+[{:(1,0,0),(0,-2,0),(0,0,-4):}]=[{:(4," "0,0),(0,-7,0),(0," "0,3):}].`
(iii) `-5A=(-5).A=(-5).[{:(3,0,0),(0,-5,0),(0,0,7):}]=[{:(-15,0," "0),(0,25," "0),(0,0,-35):}].`
(iv)`2A+3B=[{:(6,0,0),(0,-10,0),(0,0,14):}]+[{:(-3,0,0),(0,6,0),(0,0,12):}]=[{:(3,0,0),(0,-4,0),(0,0,26):}].`


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