If  show that  from Mathematics Determinants

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 Multiple Choice QuestionsShort Answer Type

171.

If straight A space equals open square brackets table row 2 cell space space space space space space space 3 end cell row 5 cell space space space minus 2 end cell end table close square brackets, show that straight A to the power of negative 1 end exponent space equals space 1 over 19 straight A.

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172.

Let A be the matrix open square brackets table row 3 cell space space 8 end cell row 2 cell space space 1 end cell end table close square brackets. Find –1 and verify that straight A to the power of negative 1 end exponent space equals space 1 over 13 straight A space minus space 4 over 13 straight I
where I is 2 × 2 unit matrix.

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173.

If A = open square brackets table row 2 cell space space space 5 end cell row 1 cell space space space 6 end cell end table close square brackets comma   find straight A to the power of negative 1 end exponent and verify that straight A to the power of negative 1 end exponent space equals space minus 1 over 7 straight A plus 8 over 7 straight I

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174.

Given straight A space equals space open square brackets table row 2 cell space space space space space minus 3 end cell row cell negative 4 end cell cell space space space space space space space 7 end cell end table close square brackets comma compute A–1 and show that 2A–1 = 9 I – A.

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175.

Find the inverse of  straight A space equals space open square brackets table row 3 cell space space space space space space space 5 end cell row 7 cell space space minus 11 end cell end table close square brackets and verify that AA–1 = I.

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176.

For what values of x, is the following matrix singular?
open square brackets table row cell 3 minus 2 straight x end cell cell space space space space straight x plus 1 end cell row 2 cell space space space space 4 end cell end table close square brackets

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177. For what value of    ‘a’ is the matrix
open square brackets table row 4 cell space minus 3 end cell cell space space space space space minus 1 end cell row 2 cell space space space space space straight a end cell cell space space space space space space space space 6 end cell row 3 cell space space minus 5 end cell cell space space space minus 4 end cell end table close square brackets
singular?
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 Multiple Choice QuestionsLong Answer Type

178.

If straight A space equals space open square brackets table row 3 cell space space space space space 1 end cell row 7 cell space space space space space 5 end cell end table close square brackets comma find x and y find that A2 + xI = y A. Hence find A–1

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179.

If straight A space equals space open square brackets table row 6 cell space space space space 5 end cell row 7 cell space space space space 6 end cell end table close square brackets comma show that A2 – 12A + I = O. Hence find A –1.

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 Multiple Choice QuestionsShort Answer Type

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180.

If straight A space equals space open square brackets table row 2 cell space space space 7 end cell row 1 cell space space space 4 end cell end table close square brackets comma space space show that straight A squared minus 6 straight A space plus space straight I space equals space straight O comma space hence space find space straight A to the power of negative 1 end exponent.


straight A space equals open square brackets table row 2 cell space space space space 7 end cell row 1 cell space space space 4 end cell end table close square brackets
therefore space space space straight A squared space equals space open square brackets table row 2 cell space space space space 7 end cell row 1 cell space space space 4 end cell end table close square brackets space open square brackets table row 2 cell space space space 7 end cell row 1 cell space space space 4 end cell end table close square brackets space equals space open square brackets table row cell 4 plus 7 end cell cell space space space 14 plus 28 end cell row cell 2 plus 4 end cell cell space space 7 plus 16 end cell end table close square brackets space equals space open square brackets table row 11 cell space space 42 end cell row 6 cell space space 23 end cell end table close square brackets
therefore space space space space straight A squared minus 6 straight A plus straight I space equals open square brackets table row 11 cell space space space space 42 end cell row 6 cell space space 23 end cell end table close square brackets space minus space open square brackets table row 2 cell space space space space 7 end cell row 1 cell space space space 4 end cell end table close square brackets space plus space open square brackets table row 1 cell space space space 0 end cell row 0 cell space space space 1 end cell end table close square brackets
space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space open square brackets table row 11 cell space space 42 end cell row 6 cell space 23 end cell end table close square brackets space plus space open square brackets table row cell negative 12 end cell cell space space space minus 42 end cell row cell negative 6 end cell cell space space minus 24 end cell end table close square brackets space plus space open square brackets table row 1 cell space space space 0 end cell row 0 cell space space space 1 end cell end table close square brackets

                         equals space open square brackets table row cell 11 minus 12 plus 1 end cell cell space space space 42 minus 42 plus 0 end cell row cell 6 minus 6 plus 0 end cell cell space space space 23 minus 24 plus 1 end cell end table close square brackets space equals space open square brackets table row 0 cell space space 0 end cell row 0 cell space space 0 end cell end table close square brackets

therefore space space space space space straight A squared minus 6 straight A plus straight I space equals space straight O space space space space space space space space space space space space space space space space space space space space space space space space rightwards double arrow space space space straight I space equals space minus straight A squared plus 6 straight A
rightwards double arrow space space space space space straight I thin space straight A to the power of negative 1 end exponent space equals space minus straight A squared straight A to the power of negative 1 end exponent space plus space 6 AA to the power of negative 1 end exponent space space space space space space rightwards double arrow space space straight A to the power of negative 1 end exponent space equals space minus straight A space plus space 6 thin space straight I
therefore space space space space space space space straight A to the power of negative 1 end exponent space equals space minus open square brackets table row 2 cell space space space 7 end cell row 1 cell space space 4 end cell end table close square brackets plus 6 space open square brackets table row 1 cell space space space 0 end cell row 0 cell space space space 1 end cell end table close square brackets space equals space open square brackets table row cell negative 2 end cell cell space space space minus 7 end cell row cell negative 1 end cell cell space space minus 4 end cell end table close square brackets space plus space open square brackets table row 6 cell space space 0 end cell row 0 cell space space 6 end cell end table close square brackets
space space space space space space space space space space space space space space space space space space space equals space open square brackets table row cell negative 2 plus 6 end cell cell space space space space space space minus 7 plus 0 end cell row cell negative 1 plus 0 end cell cell space space space space space minus 4 plus 6 end cell end table close square brackets space equals space open square brackets table row cell space space 4 end cell cell space space space minus 7 end cell row cell negative 1 end cell cell space space space space space 2 end cell end table close square brackets
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