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Differential Calculus> tangents and normals at what points will ...

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tangents and normals
at what points will the tangents to the curve y = 2x^3 – 15x^2 + 36x – 21 be parallel to x axis? also find the equations of the tangents to the curve at these points

taniska , 11 Years ago

Grade 12

1 Answers

Jitender Singh

Ans:
Hello Student,
Please find answer to your question below

$y = 2x^3 - 15x^2 + 36x - 21$
Slope of tangent: y’ = 0
$y' = 2.3x^2 - 15.2x + 36 = 0$
$6x^2 - 30x + 36 = 0$
$x^2 - 5x + 6 = 0$
$(x-3)(x-2) = 0$
$\Rightarrow x = 2, 3$
Find the corresponding y and thats gonna be the eauation of tangents.
x = 2
$y = 2.2^3 - 15.2^2 + 36.2 - 21$
$y = 16 - 60 + 72 - 21 = 7$
x = 3
$y = 2.3^3 - 15.3^2 + 36.3 - 21$
$y = 54 - 135 + 108 - 21 = 6$
y = 6 and y = 7 are equation of tangents.

Last Activity: 11 Years ago

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