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a point moves on the parabola y^2=16x in such a way that the rate of change of the abscissa
is always 3 units/sec. how fast is the ordinate changing when the abscissa is 1 unit?
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The point (x,y) moves x = x(t), y = y(t) along the parabola
y^2 = 16x (1)
in such a way that the rate of change of the abscissa always is = 3 units/sec.
They want you find at x = 1.
It is easy. Take the derivatives respective the time "t" of the equation (1). You will get
= , (2)
At x= 1, y^2 = 16, from equation (1). So, substitute in (2) y = +/- = +/- 4, = 3, as it is given. You will get
2*(+/-4)* = ,
which gives you
= +/- 6.
ANSWER. Under given conditions, = +/- 6.
It means that when the point (x,y) moves on the upper branch y = , = 6 at x= 1.
When the point (x,y) moves on the lower branch y = , = -6 at x= 1.
Solved.