Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
CALCULUS HELP?? the graph of the function f(x)=x^3+px^2+qx has a point of?
the graph of the function f(x)=x^3+px^2+qx has a point of inflection at (2,-22). determine exactly the constants p and q
4 Answers
- Chandler BingLv 69 years agoFavorite Answer
f(x) = x³ + px² + qx
The point (2,-22) is on the graph. This means that f(2) = -22.
f(2) = 8 + 4p + 2q = -22 ==> 4p+2q = -30....(1)
Since this is an inflection point, f '' (2) = 0.
f ' (x) = 3x² + 2px
f ''(x) = 6x + 2p
f '' (2) = 12+2p = 0 ==> 2p = -12 ==> p = -6
Plug p=-6 into (1):
-24 + 2q = -30 ==> 2q =-6 ==> q = -3
- Roll-Moon-ZeroLv 69 years ago
derivative equations f(x) = x^3 + px^2 + qx
f'(x) = 3x^2 +2px
f''(x) = 6x + 2p
when f''(x) = 0
6x + 2p = 0
<=> 6x = - 2p
<=> x = - p/3
I has a point of inflection at (2,-22) => x = -p/3 = 2
=> p = - 6
Replace p =- 6 in f(x) = x^3 + px^2 + qx
f(x) = x^3 - 6x^2 + qx (*)
at this replace A (2 ; -22) in (*) with y = f(2) = -22
-22 = 8 - 6.4 + 2q
-22 = 2q - 16
2q = -6
=> q = - 3
So p = -6 , q = -3 the graph of the function f(x)=x^3+px^2+qx has a point of inflection at (2,-22)
- Moise GunenLv 79 years ago
x-axis value of inflection points are root of the 2nd derivative then:
f ' ' (x) = 6x +2p = 0 then
f ' ' (2) = 6*2+2p =0 then p = -6
Now f(x) = x^3 - 6x^2 +qx and f(2) = -22
8 - 24 +2q = 22
q = 19
f (x) = x^3 - 6x^2 + 19x
- strombergLv 45 years ago
First change ( x=2, y= -22 ) to get the first eq 8 +4p +2q = - 22 ( eq a million) inflection aspect exhibits the 2d spinoff f ' ' ( x) = 6 x +2p = 0 and 0 = 12 + 2p ( eq 2 ) remedy equipment (a million) and (2) ==> ( p= -6 ,q = - 3 )