Show that the function f (x) = x2 is an increasing function in

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 Multiple Choice QuestionsMultiple Choice Questions

131.

The slope of the normal to the curve y = 2 x2 + 3 sin x at x = 0 is

  • 3

  • 1 third
  • -3

  • -3

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132.

The line y = x + 1 is a tangent to the curve y 2 = 4x at the point

  • (1, 2)

  • (2, 3)

  • (1, -2)

  • (1, -2)

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133. The normal at the point (1, 1) on the curve 2y + x2 = 3 is
  • x + y = 0
  • x – y = 0
  • x + y + 1 = 0
  • x + y + 1 = 0
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134. The normal to the curve x2 = 4 y passing (1, 2) is
  • x + y = 3 
  • x – y = 3
  • x + y = 1
  • x + y = 1
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 Multiple Choice QuestionsShort Answer Type

135. Show that the function f (x) = 2 x + 3 is a strictly increasing function on R.
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136. Without using the derivative show that the function f (a) = 7x – 3 is a strictly increasing function on R.
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137. Show that the function f (x) = x2 is an increasing function in (0, ∞).


Let x1 , x2 ∊ (0, ∞) and let x1, < x2.
Now,      straight x subscript 1 space less than space straight x subscript 2
rightwards double arrow space space space space space straight x subscript 1. space straight x subscript 1 space space space less than space straight x subscript 1. space straight x subscript 2                                                          open square brackets because space space straight x subscript 1 greater than 0 close square brackets

rightwards double arrow space space space space straight x subscript 1 squared space space less than space straight x subscript 1. straight x subscript 2                                                                           ...(1)
Again     straight x subscript 1 less than straight x subscript 2
rightwards double arrow space space space space space straight x subscript 1. space space straight x subscript 2 space space space less than space space straight x subscript 2. space straight x subscript 2 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 space space space                            open square brackets because space space straight x subscript 2 space greater than space 0 close square brackets
rightwards double arrow space space space straight x subscript 1. space end subscript straight x subscript 2 space space less than space straight x subscript 2 squared                                                                            ...(2)
From (1) and (2),   we get,    straight x subscript 1 squared space less than space straight x subscript 2 squared space space space space space space or space space space space space straight f left parenthesis straight x subscript 1 right parenthesis space less than space straight f left parenthesis straight x subscript 2 right parenthesis
therefore space space straight x subscript 1 space less than space straight x subscript 2 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 space straight f left parenthesis straight x subscript 1 right parenthesis space less than space straight f left parenthesis straight x subscript 2 right parenthesis
therefore space space space space straight f space is space an space increasing space function space in space left parenthesis 0 comma space infinity right parenthesis.                                      
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138.

Show that the function f(x) = x2 is a decreasing function in (– ∞  0).

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139.

Construct an example of a functions which is strictly increasing but whose derivative vanishes at a point in the domain of definition of the function.

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140.

Prove that the exponential function ex is strictly increasing on R.

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