The curve whose equation is y=ax^3 + bx^2 + cx + d has a point of inflexion at (-1,4), a turning point when x=2, and it passes through the point (3,-7). Find the values of a, b, c and d.

Question

anonymous · Answer

a=1
b=-3
c=-6
d=11

i think this is the answer.

anonymous · Answer

would you please explain it?

anonymous · Answer

u need to differentiate y with respect to x.
point of inflexion and turning point hav dy/dx=0
then u can manipulate the infos given to get b,c,d in term of a.
so, u let a=1, u wil get the others.

anonymous · Answer

I think a=3/11   b=9/11   c=-72/11     d=-23/11

anonymous · Answer

the point of inflection implis the 2nd derivative is 0 not the first

anonymous · Answer

really? i thought because the tangent is zero, so it also implies the first derivative is zero. idk, i got it wrong. lol.. thanks twhite.

anonymous · Answer

hmmm...got it twhitelsu....thanks both of you... :)