Answer :
The pressure above the water is 15 lb/in^2 and for every 10 ft, the pressure rises 4.54 lb/in^2
The equation would be:
[tex]f(x)=4.54\frac{lb}{IN^2}\cdot10ft\cdot x+15\frac{lb}{IN^2}[/tex]If x = 0, the pressure in the surface is 15 lb/in^2, for each 10 ft of x, the pressure rises 4.54 lb/in^2
Now to solve when the pressure is 80 lb/in^2, we subtitute in the equation:
[tex]80\frac{lb}{IN^2}=4.54\frac{lb}{IN^2}\cdot10ft\cdot x+15\frac{lb}{IN^2}[/tex]And solve for x:
[tex]\begin{gathered} (80-15)\frac{lb}{IN^2}=4.54\frac{lb}{\text{IN}^2}\cdot10ft\cdot x \\ \frac{65\frac{lb}{IN^2}}{45\frac{lb}{IN^2}\cdot10ft}=x \\ \frac{1.4317}{ft}=x \\ \end{gathered}[/tex]Then the answer to question 2 is 1.43ft
This is basically a linear equation. The slope is the 4.54lb/in^2 for each 10ft. Then we need to adjust the 10ft of x, to reprensents each step of 10 ft for x. And we need to add the 15lb/in^2 for the surface pressure. With all this, we can construct the function of the pressure dependant of the deepness x.