We are given

where
y is the cost in dollars
x is distance in dollars
now, we can find derivative



so,

So,
the rate of change of the cost in dollars with respect to the number of miles is 1.5.........Answer
Step-by-step explanation:
x - 7 < -20
x < -20 + 7
x < -13
X = (-12, -11, -10,...)
So, f[x] = 1/4x^2 - 1/2Ln(x)
<span>thus f'[x] = 1/4*2x - 1/2*(1/x) = x/2 - 1/2x </span>
<span>thus f'[x]^2 = (x^2)/4 - 2*(x/2)*(1/2x) + 1/(4x^2) = (x^2)/4 - 1/2 + 1/(4x^2) </span>
<span>thus f'[x]^2 + 1 = (x^2)/4 + 1/2 + 1/(4x^2) = (x/2 + 1/2x)^2 </span>
<span>thus Sqrt[...] = (x/2 + 1/2x) </span>
17+6=23 that is the answer