1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Home school Calculas( high school level)

  1. May 6, 2007 #1
    Hi.. New at this site, hope I'm posting these stuff on the write place....
    well i had these question below for review for an exam, hope someone can help me solve them, i did my solution in Paint program and on paper and am linking where i uploaded them, ( image shack)

    -Find the second derivative
    http://img519.imageshack.us/img519/1610/pictureorvideo004sf6.th.jpg [Broken]

    ** for where 'e^-x' i think the question is wrong,, i think it should be e^x, not sure??
    http://img340.imageshack.us/img340/6392/pictureorvideo005fp2.th.jpg [Broken]

    3)Find the second derivative of 'y' with respect to "x" where
    http://img340.imageshack.us/img340/6238/pictureorvideo007rt7.th.jpg [Broken]

    4)Find the equation of 2 lines, each of slope 5, that are tangent to y=x^3+2X

    5) Find the asymptotes for

    6)A dragster accelerates down a strip adn then brakes, adn comes to stop. Its position function, s(t) is given by s(t)=3t^2-1/5t^3, s'(t) in meters, 't' in seconds
    a) when does the dragster come to a stop
    b) how far has the dragster traveled.
    http://img340.imageshack.us/img340/8870/5aso0.th.png [Broken]

    7) Find the polynomial with second degree that goes through (1,-1) and whose slope is 1, When x=-1 and where slop is 19, when x=2
    http://img457.imageshack.us/img457/3368/pictureorvideo003mp2.th.jpg [Broken]

    8) A helicopter takes off from landing pad at 10:48AM and travels south at 150KM/h is planning to land at 10:56AM.
    a) how far is the distance between them changing at 10:50AM( to 2 decimal place)
    b) Is the distance between them increasing or decreasing at this instant?

    I couldn't answer 4,5,8... please help me with them...and check solution
    thank you ...
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. May 6, 2007 #2
    For #4, the derivative is a quadratic. There are 2 places where the tan line has a slope of 5. Find the points where it equals 5 (or where that minus 5 equals zero) and then you have 2 points and 2 slopes
  4. May 6, 2007 #3
    8. If he's traveling at 150 km/h, then that's how fast the distance is changing. For b, it depends. If it went past his destination before 10:50, then the distance is increasing, otherwise it's decreasing.
  5. May 6, 2007 #4
    For quadratic equation i would need a,b and c. but i have only 2 numbers......and how would i find the point where the point equals 5?

    Also can anyone check the solutions i did,

  6. May 7, 2007 #5


    User Avatar
    Science Advisor

    "For quadratic equation i would need a,b and c. but i have only 2 numbers......and how would i find the point where the point equals 5? "
    A "point" can't equal 5! You are looking for the value of x such that the derivative 3x2+ 2= 5. Surely you can solve that equation.
  7. May 7, 2007 #6
    For #1 the final answer(first derivative) is [tex](e^{4x} \cdot 2x^2) \cdot (4x+3)[/tex] not 2x + 3...you multiplyed by 2 insted 4...

    Edit...even more simple it is if you leave it like this [tex]6x^2 e^{4x} + 8x^3 e^{4x}[/tex] and make a second derivative...
    Last edited: May 7, 2007
  8. May 7, 2007 #7
    I factored out the 2x^2, if you factor it back in , you get the same result....So confused,,,dont know where i made mistake sorry sorry,,,,,,,could you show me where i made the mistake,,,

    thank you everyone for your help:)
  9. May 10, 2007 #8
    You multiplied it wrongly...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook