Answer:
Well, one way to use reasonableness is to estimate the answer to see if your answer is an outrageous answer or not. So, looking at your problem, you see that you are multiplying a two hundred something number by 4 and then subtracting 10 from it.
Step-by-step explanation:
It should be 21 20. Sorry if I got it wrong
Let the length of side AB be $x$, then

Therefore, the perimeter of ABCDE is 2(12) + 2(4) + 6 = 24 + 8 + 6 = 38 in.
Answer:
NOT a function
Step-by-step explanation:
a function exists when every unique x input has a unique y output.
here every x less than 0 has two y values.
You'll need to use differentiation (specifically, implicit differentiation) here.
If x^2 = 4(y+6), differentiating both sides with respect to time t produces the following:
2x (dx/dt) = 4([dy/dt]) (note that (d/dt) 6 = 0)
We need to solve for (dx/dt). Substitute 8 for x (y does not appear in this latest equation, so we do nothing with y=10). Substitute the given 5 units/sec for dy/dt:
2(8)(dx/dt) = 4(5)(units/sec)
Solving for dx/dt, dx/dt = [20 units/sec]/16, or 5/4 units/sec, or 1.25 units/sec.