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This is a question for some calculus h/w that i have. here is the exact question:
Two tangents to the graph of y=(x^2-1)^2 are perpendicular to the line x+5=0. Determine the equations of the tangents.

the answer at the back of the book says y=0 and y=1, which, to me, dosn't even make sense... i have a quix on it on monday so i really need to know how to do it :) ty!

2007-04-27 06:26:24 · 4 answers · asked by Anonymous in Science & Mathematics Mathematics

4 answers

y = (x^2-1)^2 = x^4 - 2x^2 + 1

dy/dx = 4x^3 - 4x = 4x(x+1)(x-1)
= 0 when x=0, x = 1 or x = -1
x = 1 y = 0 (same as x=-1)
x = 0 y = 1
The line x+5 = 0 is the line x=-5 i.e vertical - this is why you need the derivative to be equal to 0 i.e. horizontal and horizontal lines are give by the equation y = constant

2007-04-27 06:43:07 · answer #1 · answered by welcome news 6 · 0 0

The line x + 5 = 0 is a vertical line. So you are looking for tangent lines perpendicular to this. They will be horizontal lines. Take the derivative of the function and set it equal to zero. The points where the derivative is zero will have horizontal tangents.

y = (x² - 1)²

dy/dx = 2(x² - 1)(2x) = 4x(x² - 1) = 4x(x - 1)(x + 1) = 0
x = -1, 0, 1

Solving for y at each of these points we have:
(-1,0), (0,1), and (1,0)

So the tangents to the curve at these points are:

y = 0 and y = 1.

Note that the line y = 0 is tangent to two of the points.

2007-04-27 10:22:29 · answer #2 · answered by Northstar 7 · 0 0

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2016-12-04 23:21:57 · answer #3 · answered by ? 4 · 0 0

If abc is equal to def. then xwy :/ e=MC2. You cant go wrong

2007-04-27 06:34:52 · answer #4 · answered by tod m 2 · 0 1

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