An airplane begins its descent at 1 1/2 miles above the ground. After 15 minutes, the airplane is mile above the ground. Find the change in height of the airplane. If the airplane continues to descend at this rate, how long does the entire descent last?

45 minutes

Step-by-step explanation:

If its 1 mile above the ground in 15 min from 1 ½, that means it descended ½ mile in 15 min, and if you multiply ½*3, you get 1 ½ miles, so multiply 15 minute * 3 and it would take 45 minutes for the entire descent to last

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204