A)
![g=f'](https://tex.z-dn.net/?f=g%3Df%27)
is continuous, so
![f](https://tex.z-dn.net/?f=f)
is also continuous. This means if we were to integrate
![g](https://tex.z-dn.net/?f=g)
, the same constant of integration would apply across its entire domain. Over
![0](https://tex.z-dn.net/?f=0%3Cx%3C1)
, we have
![g(x)=2x](https://tex.z-dn.net/?f=g%28x%29%3D2x)
. This means that
![f_{0](https://tex.z-dn.net/?f=f_%7B0%3Cx%3C1%7D%28x%29%3D%5Cdisplaystyle%5Cint2x%5C%2C%5Cmathrm%20dx%3Dx%5E2%2BC)
For
![f](https://tex.z-dn.net/?f=f)
to be continuous, we need the limit as
![x\to1^-](https://tex.z-dn.net/?f=x%5Cto1%5E-)
to match
![f(1)=3](https://tex.z-dn.net/?f=f%281%29%3D3)
. This means we must have
![\displaystyle\lim_{x\to1}x^2+C=1+C=3\implies C=2](https://tex.z-dn.net/?f=%5Cdisplaystyle%5Clim_%7Bx%5Cto1%7Dx%5E2%2BC%3D1%2BC%3D3%5Cimplies%20C%3D2)
Now, over
![x](https://tex.z-dn.net/?f=x%3C-2)
, we have
![g(x)=-3](https://tex.z-dn.net/?f=g%28x%29%3D-3)
, so
![f_{x](https://tex.z-dn.net/?f=f_%7Bx%3C-2%7D%28x%29%3D-3x%2B2)
, which means
![f(-5)=17](https://tex.z-dn.net/?f=f%28-5%29%3D17)
.
b) Integrating over [1, 3] is easy; it's just the area of a 2x2 square. So,
![\displaystyle\int_1^6g(x)=4+\int_3^62(x-4)^2\,\mathrm dx=4+6=10](https://tex.z-dn.net/?f=%5Cdisplaystyle%5Cint_1%5E6g%28x%29%3D4%2B%5Cint_3%5E62%28x-4%29%5E2%5C%2C%5Cmathrm%20dx%3D4%2B6%3D10)
c)
![f](https://tex.z-dn.net/?f=f)
is increasing when
![f'=g>0](https://tex.z-dn.net/?f=f%27%3Dg%3E0)
, and concave upward when
![f''=g'>0](https://tex.z-dn.net/?f=f%27%27%3Dg%27%3E0)
, i.e. when
![g](https://tex.z-dn.net/?f=g)
is also increasing.
We have
![g>0](https://tex.z-dn.net/?f=g%3E0)
over the intervals
![0](https://tex.z-dn.net/?f=0%3Cx%3C4)
and
![x>4](https://tex.z-dn.net/?f=x%3E4)
. We can additionally see that
![g'>0](https://tex.z-dn.net/?f=g%27%3E0)
only on
![0](https://tex.z-dn.net/?f=0%3Cx%3C1)
and
![x>4](https://tex.z-dn.net/?f=x%3E4)
.
d) Inflection points occur when
![f''=g'=0](https://tex.z-dn.net/?f=f%27%27%3Dg%27%3D0)
, and at such a point, to either side the sign of the second derivative
![f''=g'](https://tex.z-dn.net/?f=f%27%27%3Dg%27)
changes. We see this happening at
![x=4](https://tex.z-dn.net/?f=x%3D4)
, for which
![g'=0](https://tex.z-dn.net/?f=g%27%3D0)
, and to the left of
![x=4](https://tex.z-dn.net/?f=x%3D4)
we have
![g](https://tex.z-dn.net/?f=g)
decreasing, then increasing along the other side.
We also have
![g'=0](https://tex.z-dn.net/?f=g%27%3D0)
along the interval
![-1](https://tex.z-dn.net/?f=-1%3Cx%3C0)
, but even if we were to allow an entire interval as a "site of inflection", we can see that
![g'>0](https://tex.z-dn.net/?f=g%27%3E0)
to either side, so concavity would not change.