Question

A square with side x is changing with time where x(t)=3t+1. What is rate of change of the area of the square when t=2 seconds.

Answer 1

Answer:

Rate of change of the area of the square is 42 units at t = 2.

Step-by-step explanation:

We note that the area of the square is given by: $A(x) = x^2$ but we aim to find $\frac{dA}{dt}$. But we can use the chain rule to pull out that dA/dt. Doing so gives us:

$\frac{dA}{dt} = \frac{dA}{dx} \times \frac{dx}{dt}.$

Now, $\frac{dA}{dx} = 2x$ (by the power rule and $\frac{dx}{dt} = 3.$

But since we have "x" and not "t", we want to find what x is when t = 2. Substituting t = 2 gives us x(2) = 3(2) + 1 = 7.

So, finally, we see that:

$\frac{dA}{dt} = 2(7) \times 3 = 14 \times 3 = 42.$