If y = √(2x + 1), then differentiating both sides implicitly with respect to t gives
dy/dt = 1/2 • 1/√(2x + 1) • 2 • dx/dt = 1/√(2x + 1) • dx/dt
(a) If dx/dt = 9 and x = 4, then
dy/dt = 1/√(2•4 + 1) • 9
dy/dt = 1/√(8 + 1) • 9
dy/dt = 1/√9 • 9
dy/dt = 9/3
dy/dt = 3
(b) If dy/dt = 3 and x = 40, then
3 = 1/√(2•40 + 1) • dx/dt
3 = 1/√(80 + 1) • dx/dt
3 = 1/√81 • dx/dt
3 = 1/9 • dx/dt
dx/dt = 27
Using the given information, we can say the following:
Width (W) = x
Length (L) = (2x - 4)
Area of Rectangle = L × W
Using this, we can formulate an equation for rectangle in question:
x(2x - 4) = 30
Expand and move everything to one side:
2x² - 4x - 30 = 0
Simplify by dividing everything on both sides by 2:
x² - 2x - 15 = 0
Factorise:
(x + 5)(x - 3) = 0
Set each factor equal to 0 and solve for x:
x + 5 = 0
x = -5 (a dimension cannot be negative so this is not the solution we want)
x - 3 = 0
x = 3 (this is the solution)
x = W = 3"
L = 2x - 4
L = 2(3) - 4
L = 2"
So, the length the rectangle is 2" and the width is 3"
28 divided by 1.0000 is 20
Answer:
There must he a circulation. May not be causation.
