Using properties of determinants, prove that  from Class 12 CB

Subject

Mathematics

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

1.

If A is a 3 × 3 invertible matrix, then what will be the value of k if det(A–1) = (det A)k.

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2.

Determine the value of the constant ‘k’ so that the function  is continuous at x = 0.

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3.

If a line makes angles 90° and 60° respectively with the positive directions of x and y axes, find the angle which it makes with the positive direction of the z-axis.

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4.

Show that all the diagonal elements of a skew symmetric matrix are zero.

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5.
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6.

The volume of a sphere is increasing at the rate of 3 cubic centimetres per second. Find the rate of increase of its surface area, when the radius is 2 cm.

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7.

Show that the function f(x) = 4x3 – 18x2 + 27x – 7 is always increasing on R.

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8.

Prove that 

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9.

Using properties of determinants, prove that 


open vertical bar table row cell straight x space end cell cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell row cell straight x plus 2 straight y space end cell cell straight x space end cell cell straight x plus straight y end cell row cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell cell straight x space end cell end table close vertical bar
Applying space straight R subscript 1 rightwards arrow straight R subscript 1 space plus straight R subscript 2 space plus space straight R subscript 3 space we space get colon
open vertical bar table row cell 3 left parenthesis straight x plus straight y right parenthesis end cell cell 3 left parenthesis straight x plus straight y right parenthesis end cell cell 3 left parenthesis straight x plus straight y right parenthesis end cell row cell straight x plus 2 straight y end cell straight x cell straight x plus straight y end cell row cell straight x plus straight y end cell cell straight x plus 2 straight y end cell straight x end table close vertical bar
space equals space 3 left parenthesis straight x plus straight y right parenthesis space open vertical bar table row 1 1 1 row cell straight x plus 2 straight y end cell straight x cell straight x plus straight y end cell row cell straight x plus straight y end cell cell straight x plus 2 straight y end cell straight x end table close vertical bar
Applying space straight C subscript 1 rightwards arrow straight C subscript 1 minus straight C subscript 2 space and space straight C subscript 2 space rightwards arrow straight C subscript 2 minus straight C subscript 3 space we space get colon
3 left parenthesis straight x plus straight y right parenthesis space open vertical bar table row 0 0 1 row cell 2 straight y end cell cell negative straight y end cell cell straight x plus straight y end cell row cell negative straight y end cell cell 2 straight y end cell straight x end table close vertical bar
equals space 3 left parenthesis straight x plus straight y right parenthesis open vertical bar table row cell 2 straight y end cell cell negative straight y end cell row cell negative straight y end cell cell 2 straight y end cell end table close vertical bar space equals space 3 left parenthesis straight x plus straight y right parenthesis left parenthesis 4 straight y squared minus straight y squared right parenthesis space equals space 9 straight y squared space left parenthesis straight x plus straight y right parenthesis
space RHS equals space LHS
Hence space Proved
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10.

Let find a matrix D such that CD – AB = O.

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