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The differentiable functions 
x and 
y are related by the following equation:

y=sqrtx
Also, 
(dx)/(dt)=12.
Find 
(dy)/(dt) when 
x=9.

The differentiable functions x x and y y are related by the following equation:\newliney=x y=\sqrt{x} \newlineAlso, dxdt=12 \frac{d x}{d t}=12 .\newlineFind dydt \frac{d y}{d t} when x=9 x=9 .

Full solution

Q. The differentiable functions x x and y y are related by the following equation:\newliney=x y=\sqrt{x} \newlineAlso, dxdt=12 \frac{d x}{d t}=12 .\newlineFind dydt \frac{d y}{d t} when x=9 x=9 .
  1. Given function and rate: We are given the function y=xy = \sqrt{x} and the rate of change of xx with respect to tt, which is dxdt=12\frac{dx}{dt} = 12. We need to find the rate of change of yy with respect to tt, which is dydt\frac{dy}{dt}, when x=9x = 9.
  2. Apply chain rule: To find dydt\frac{dy}{dt}, we can use the chain rule from calculus, which states that dydt=dydx×dxdt\frac{dy}{dt} = \frac{dy}{dx} \times \frac{dx}{dt}. We already know dxdt=12\frac{dx}{dt} = 12, so we need to find dydx\frac{dy}{dx} when x=9x = 9.
  3. Find derivative of yy: To find dydx\frac{dy}{dx}, we differentiate y=xy = \sqrt{x} with respect to xx. The derivative of x\sqrt{x} with respect to xx is 12x12\frac{1}{2}x^{-\frac{1}{2}}.
  4. Substitute x=9x=9: Now we substitute x=9x = 9 into the derivative dydx\frac{dy}{dx} to find its value at that point. dydx=12(9)12=12(19)=12(13)=16\frac{dy}{dx} = \frac{1}{2}(9)^{-\frac{1}{2}} = \frac{1}{2}(\frac{1}{\sqrt{9}}) = \frac{1}{2}(\frac{1}{3}) = \frac{1}{6}.
  5. Calculate dydt\frac{dy}{dt}: Now that we have dydx=16\frac{dy}{dx} = \frac{1}{6} and dxdt=12\frac{dx}{dt} = 12, we can use the chain rule to find dydt\frac{dy}{dt}. dydt=dydx×dxdt=16×12=2\frac{dy}{dt} = \frac{dy}{dx} \times \frac{dx}{dt} = \frac{1}{6} \times 12 = 2.

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