Find out the points on the curve  at which the tangents are (i

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 Multiple Choice QuestionsLong Answer Type

111.

Find the equation of the tangent line to the curve  y = x2 – 2x + 7 which is
(a) parallel to the line 2x – y + 9 = 0
(ii) perpendicular to the line 5y – 15y = 13

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112. Find the equations of normal lines to the curve y = x2 – 3 x which are parallel to the line x + 9y = 14.
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113. Find the equation of the normals to the curve y = x3 + 2x + 6 which are parallel to the line 14y + 4 = 0.
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114.

At what point will the tangent to the curve y = 2x3 – 15x2 + 36x – 21 be parallel to x-axis ? Also, find the equations of tangents to the curve at those points.

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 Multiple Choice QuestionsShort Answer Type

115.

Find the points on the curve x2 + y2 -2x – 3 = 0 at which the tangents are parallel to the x-axis.

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116. Find points at which the tangent to the curve y = x3 – 3x2 – 9x + 7 is parallel to the x-axis.
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117.

Find point on the curve y = 3x2 – 12x + 6 at which tangent is parallel to x-axis. Also find the equation of tangent line. 

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118.

Find out on the curve y = x2 – x – 8 at which tangent is parallel to x-axis. Also find the equation of tangent line.

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119.

Find out on the curve y = 2 x2 – 6x – 4 at which tangent is parallel to x-axis. Also find the equation of tangent line.

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 Multiple Choice QuestionsLong Answer Type

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120.

Find out the points on the curve straight x squared over 9 minus straight y squared over 16 space equals space 1 at which the tangents are (i) parallel to the x-axis and (ii) parallel to the y-axis.


 The equation of curve is  straight x squared over 9 minus straight y squared over 16 space equals space 1
Differentiating both sides w.r.t.x, we get,
                           fraction numerator 2 straight x over denominator 9 end fraction minus fraction numerator 2 straight y over denominator 16 end fraction dy over dx space equals space 0 space space space space space space or space space space space space space straight y over 8 dy over dx space equals space fraction numerator 2 straight x over denominator 9 end fraction
therefore space space space space space space space dy over dx space equals space fraction numerator 16 space straight x over denominator 9 space straight y end fraction
(i) For the points on the curve, where tangents are parallel to x-axis.
                        dy over dx space equals space 0 space space space space space rightwards double arrow space space space fraction numerator 16 straight x over denominator 9 straight y end fraction space equals space 0 space space space space rightwards double arrow space space space space straight x space equals space 0
Putting x = 0 in (1), we get,
                     0 minus straight y squared over 16 space equals space 1 space space space space space rightwards double arrow space space space space straight y squared space equals space minus 16 space space space space rightwards double arrow space space space space straight y space equals space plus-or-minus 4 space straight i
therefore  there is no real point at which the tangent is parallel to x-axis.
(ii) For the points on the curve, where tangents are parallel to y-axis.
                        dx over dy space equals space 0 space space space space space rightwards double arrow space space space space space fraction numerator 9 straight y over denominator 16 straight x end fraction space equals space 0 space space space rightwards double arrow space space space straight y space equals space 0
Putting y = 0 in (1), we get,
                     straight x squared over 9 minus 0 space equals space 1 space space space space space space space rightwards double arrow space space space space space space straight x squared space equals space 9 space space space space space space rightwards double arrow space space space space straight x space equals negative 3 comma space space 3
therefore space space space space points space are space left parenthesis negative 3 comma space 0 right parenthesis comma space space left parenthesis 3 comma space 0 right parenthesis

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