Integral R2Er
1. We are asked to find the integral $$\int (r^2 + r + 1)e^r \, dr$$.
2. To solve this, we use integration by parts, which states:
$$\int u \, dv = uv - \int v \, du$$.
3. Let’s choose parts:
- Let $$u = r^2 + r + 1$$, so $$du = (2r + 1) dr$$.
- Let $$dv = e^r dr$$, so $$v = e^r$$.
4. Applying integration by parts:
$$\int (r^2 + r + 1)e^r dr = (r^2 + r + 1)e^r - \int (2r + 1)e^r dr$$.
5. Now, we need to evaluate $$\int (2r + 1)e^r dr$$. Use integration by parts again:
- Let $$u = 2r + 1$$, so $$du = 2 dr$$.
- Let $$dv = e^r dr$$, so $$v = e^r$$.
6. Applying integration by parts again:
$$\int (2r + 1)e^r dr = (2r + 1)e^r - \int 2 e^r dr = (2r + 1)e^r - 2 \int e^r dr$$.
7. Since $$\int e^r dr = e^r$$, we have:
$$\int (2r + 1)e^r dr = (2r + 1)e^r - 2 e^r = (2r + 1 - 2)e^r = (2r - 1)e^r$$.
8. Substitute back:
$$\int (r^2 + r + 1)e^r dr = (r^2 + r + 1)e^r - (2r - 1)e^r + C = (r^2 + r + 1 - 2r + 1)e^r + C = (r^2 - r + 2)e^r + C$$.
9. Final answer:
$$\boxed{\int (r^2 + r + 1)e^r dr = (r^2 - r + 2)e^r + C}$$.
This integral was solved using integration by parts twice, carefully choosing $$u$$ and $$dv$$ each time, and simplifying the resulting expressions.