Use the definition of the definite integral to evaluate the following definite integrals. Use right Riemann sums and Theorem 5.1.
1. ₀∫²(2x + 1) dx
2. ₁∫⁵ (1 - x) dx
3. ₃∫⁷ (4x + 6) dx
4. ₀∫² (x² - 1) dx