1a find all points xy where the derivative is 0 2a Find the
1a. find all points (x,y) where the derivative is 0
2a. Find the x values where the derivative is 0
2b. Find any points of inflection
Solution
1) f(x) = -2x^2 - 12x +1
derivative : f\'(x) = -4x -12
f\'(x) =0 ; -4x -12 =0
x = -3
y = f(-3) = -2(9) - 12(-3) +1 = -18 + 36 +1 = 19
(x, y) = ( -3, 19)
2) f(x) = x^3 + 3x^2 - 9x +1
f\'(x) = 3x^2 + 6x -9
f\'(x) =0 ; 3x^2 + 6x -9 =0
x^2 + 2x -3 =0 ; x^2 + 3x -x -3 =0
(x+3)(x-1) =0
x= -3 ; x =1
Inflection point: f\"(x) = 6x + 6
f\"(x) =0 ; x= -1
f(-1) = 12
Point ( -1 , 12)
