Answer:
The answer to this question can be defined as follows:
In option A, the answer is "- 357.14 miles per hour".
In option B, the answer is "-0.98".
Step-by-step explanation:
Given:
[tex]\frac{dx}{dt} =- 300 \text{ miles per hour}[/tex]
[tex]\frac{dy}{dt} =- 400 \text{ miles per hour}[/tex]
find:
[tex]\frac{ds}{dt} =?[/tex] when
[tex]x= 150 \\y= 200\\s=x+y\\\\[/tex]
[tex]= 150+200 \\\\=350[/tex]
[tex]\to s^2=x^2+y^2\\[/tex]
differentiate the above value:
[tex]\to 2s\frac{ds}{dt}= 2x \frac{dx}{dt}+2y \frac{dy}{dt}[/tex]
[tex]\to 2s\frac{ds}{dt}= 2(x \frac{dx}{dt}+y \frac{dy}{dt})\\\\\to \frac{ds}{dt}= \frac{(x \frac{dx}{dt}+y \frac{dy}{dt})}{s}\\\\[/tex]
[tex]= \frac{(150 \times -300 +200 \times -400 )}{350}\\\\= \frac{-45000+ (-80000) }{350}\\\\= \frac{- 125000 }{350}\\\\= - 357.14 \ \text{miles per hour}[/tex]
In option B:
[tex]\to d=rt\\\\ \to t= \frac{d}{r}[/tex]
[tex]\to \ \ d= 350 \ \ \ \ \ \ r= -357.14\\[/tex]
[tex]\to t= - \frac{350}{357.14}\\\\\to t= - 0.98[/tex]
