Inflexion point question (1 Viewer)

[enigma_1]

the curve y=ax^3 +bx^2 -x+5 has a point of inflexion at (1, -2). Find the values of a and b.

Sorry I know this is probs a dumb question haha

 

[Carrotsticks]

the curve y=ax^3 +bx^2 -x+5 has a point of inflexion at (1, -2). Find the values of a and b.

Sorry I know this is probs a dumb question haha

Not a dumb question, just a question =)

Since it has a point of inflexion at x=1, we know that f''(x)=0 at x=1, so f''(1)=0.

Also, since the point (1,-2) lies on the curve, we can sub in x=1, y=-2.

You should now have two equations in terms of A and B that you can solve simultaneously.