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Primitive function (1 Viewer)

mtsmahia

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Q) A Curve has y double dash= 8x and the tangent at (-2,5) makes an angle of 45* with the x-axis. Find the equation of the curve ?

Thanks :D
 

Trebla

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Q) A Curve has y double dash= 8x and the tangent at (-2,5) makes an angle of 45* with the x-axis. Find the equation of the curve ?

Thanks :D
y'' = 8x
y' = 4x² + c
If it makes an angle of 45 degrees with the x-axis then the gradient is 1 at (-2, 5)
4(-2)² + c1 = 1
c1 = - 15
Thus
y' = 4x² - 15
y = 4x³/3 - 15x + c2
Sub (-2, 5) since it lies on the curve
5 = - 32/3 - 15(-2) + c2
c2 = - 43/3
Hence
y = 4x³/3 - 15x - 43/3

Check my working...hope that's right...
 

mtsmahia

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y'' = 8x
y' = 4x² + c
If it makes an angle of 45 degrees with the x-axis then the gradient is 1 at (-2, 5)
4(-2)² + c1 = 1
c1 = - 15
Thus
y' = 4x² - 15
y = 4x³/3 - 15x + c2
Sub (-2, 5) since it lies on the curve
5 = - 32/3 - 15(-2) + c2
c2 = - 43/3
Hence
y = 4x³/3 - 15x - 43/3

Check my working...hope that's right...
yep! its right , thanks :D
 

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