Thread: Yes, this is a homework question...

...which I know you guys don't like, but I'm really stuck. Just starting calculus wee....

Find the values of the constants a and b, that makes the differentiable at the point where the rule for the function changes.

Code:

f(x)={ax^2+10, x<2
      x^2-bx, x≥2

yea so thats like a split function.

TIA

Hey Keith

You need to remember two things here

1. If a function has a derivative at a point then it is continuous at that point. So look at the limits of f(x) as x->2 from the right and left and equate them.

2. The derivative is a limit, so it exists if its left and right limits exist. This boils down to taking the derivative of each piece seperately and equating them when x=2.

So solve these two equations and you should get your result.

I was doing that (still am) but every time I end up with the same wrong values for a and b. I get b=-10 and a=3.5. I guess I'll get it eventually.

Thanks.

EDIT:Well, it seems that is what everyone else got. It doesn't seem to check though.

EDIT2:NVM I got it!