Question

please, please, please, help me. this is 100 points. I only have 20 more minutes, if you could help that'd be amazing. Im running out of time and am really stressed. Attached is my question.

Answer 1

Answer:

Step-by-step explanation:

If you complete the square and double the time to get back to the surface you will have your answer.

 

d = 2(t^2 - 4t) - 10; Take 1/2 of - 4 and square it. Add the result inside the brackets.

d = 2(t^2 - 4t + (4/2)^2 ) - 10  

d = 2*(t^2 - 4t + 4) - 10 - 2*4  

Did you notice I put the 2*4 outside the brackets and turned it into a minus. The reason that happened is to offset what is inside the brackets that was added here.

d = 2(x - 2)^2 - 18; t^2 - 4t + 4 is a perfect square. that 2 inside the brackets is critically important.  

The 18 is the maximum depth below the surface of the water. (Poor choice of words. Technically - 18 is a minimum). But you want to use t - 2 to make it into 0.     t - 2 = 0 ; t =2  

What that means is that it took 2 minutes to get 18 meters below the surface of the water. He will break the surface of the water 2 minutes later. I don't exactly know how to answer the question. It is 2 minutes to get from the minimum depth to the surface. It is 4 minutes to get to the surface when he begins his dive.