Posted by **Mike** on Wednesday, April 15, 2009 at 10:38pm.

Find an equation of the tangent line to the parabola at the given point, and find the x-intercept of the line.

17) x^2=2y , (-3,9/2)

18) y=-2x^2 , (-1,-2)

- Pre-Cal -
**drwls**, Thursday, April 16, 2009 at 12:57am
I'll do one of them. Use the same method for the other.

17) y = x^2/2 and the slope of the parabola is dy/dx = x

When x = -3, y = 9/2 and the slope is -3. A straight line going through (-3, 9/2) with slope -3 has the equation

y - 9/2 = -3[x -(-3)]

y = -3x + 9/2 -9 = -3x -9/2

The x intercept (where y = 0) is

x = -3/2

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