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Let A=[{:(1,-2,3),(-4,2,5):}]" and "B=[{...

Let `A=[{:(1,-2,3),(-4,2,5):}]" and "B=[{:(2,3),(4,5),(-2,1):}].` Find AB and BA, and show that `ABneBA.`

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Here A is a `2xx3` matrix and B is a `3xx2` matrix.
So, AB exists and it is a `2xx2` matrix.
Now, `AB=[{:(1,-2,3),(-4," "2,5):}][{:(2,3),(4,5),(-2,1):}]`
`=[{:(1.2+(-2).4+3.(-2),1.3+(-2).5+3.1),((-4).2+2.4+5.(-2),(-4).3+2.5+5.1):}]`
`=[{:(-12,-4),(-10," "3):}].`
Again, B is a `3xx2` matrix and A is a `2xx3` matrix.
So, BA exists and it is a `3xx3` matrix.
Now, `BA=[{:(2,3),(4,5),(-2,1):}][{:(1,-2,3),(-4," "2,5):}]`
`=[{:(2.1+3.(-4),2.(-2)+3.2,2.3+3.5),(4.1+5.(-4),4.(-2)+5.2,4.3+5.5),((-2).1+1.(-4),(-2).(-2)+1.2,(-2).3+1.5):}]`
`=[{:(-10,2,21),(-16,2,37),(-6,6,-1):}].`
Hence, `ABneBA.`
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RS AGGARWAL-MATRICES-Exercise 5F
  1. Let A=[{:(1,-2,3),(-4,2,5):}]" and "B=[{:(2,3),(4,5),(-2,1):}]. Find A...

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  2. Construct a 2xx3 matrix whose elements are given by a(ij)=(1)/(2)(i-...

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  3. Construct a 2xx3 matrix whose elements are given by a(ij)=(1)/(2)|-3...

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  4. If [{:(x+2y,-y),(3x,4):}]=[{:(-4,3),(6,4):}], find the values of x and...

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  5. Find the values of x and y, if 2[{:(1,3),(0,x):}]+[{:(y,0),(1,2) :}]...

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  6. If x.[{:(2),(3):}]+y.[{:(-1),(1):}]=[{:(10),(5):}], find the values of...

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  7. If [{:(x,3x-y),(2x+z,3y-w):}]=[{:(3,2),(4,7):}], find the values of w...

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  8. If [{:(x,6),(-1,2w):}]+[{:(" "4,x+y),(z+w," "3):}]=3[{:(x,y),(z,w):}],...

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  9. If A=" diag "(3" "-2" "5)" and "B=" diag "(1" "3" "-4)," find "(A+B).

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  10. Show that costheta.[{:(costheta,sintheta),(-sintheta,costheta):}]+sint...

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  11. If A=[{:(1,-5),(-3," "2),(4,-2):}]" and "B=[{:(3," "1),(2,-1),(-2," "3...

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  12. If A=[{:(cosalpha,-sinalpha),(sinalpha,cosalpha):}], then find the lea...

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  13. Find the values of x and y for which [{:(2,-3),(1," "1):}][{:(x),(y)...

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  14. Find the values of x and y for which [{:(x,y),(3y,x):}][{:(1),(2):}]...

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  15. If A=[{:(4,5),(1,8):}], show that (A+A') is symmetric.

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  16. If A=[{:(2,3),(4,5):}], show that (A-A') is skew-symmetric.

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  17. If A=[{:(2,-3),(4," "5):}]" and "B=[{:(-1,2),(0,3):}], find a matrix X...

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  18. If A=[{:(4,2),(1,3):}]" and "B=[{:(-2,1),(3,2):}], find a matrix X suc...

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  19. If (i) A=[cosalphasinalpha-sinalphacosalpha] , then verify that Aprime...

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  20. If A and B are two symmetric matrix of same order, then show that (AB-...

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  21. If f(x)=x^2-4x+1 then find f(A) when A=[[2,3] , [1,2]]

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