Determine the equation of both lines that are tangent to the graph of y=x^2 +4 and pass through the point (1,-2)
So would I simply use the y=mx+b form, m=2, y= -2, and x = 1?
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Determine the equation of both lines that are tangent to the graph of y=x^2 +4 and pass through the point (1,-2)
So would I simply use the y=mx+b form, m=2, y= -2, and x = 1?
no ... the point (1,-2) does not lie on the parabola.Quote:
Originally Posted by RyGuy
Oh right.Quote:
Originally Posted by skeeter
So then how would I go about this?
the derivative of the parabola equation gives the slope of all tangent lines to the curve.Quote:
Originally Posted by RyGuy
You need the equations of the two that pass through (1,-2).
hence, write the derivative to get the slopes of these lines.
then use
point of tangency on the curve is
each tangent line passes thru the point
remember how to find the slope between two points?
... also, note that the slope of both tangent lines is y' = 2x
I'll let you take it from here.