Summation Properties
1. We are given two summation expressions and need to verify their correctness.
2. First, consider the summation $$\sum_{r=1}^3 (3r + 4)$$.
3. According to the summation property, this can be split as:
$$\sum_{r=1}^3 (3r + 4) = \sum_{r=1}^3 3r + \sum_{r=1}^3 4$$
4. Evaluate each summation separately:
- $$\sum_{r=1}^3 3r = 3(1) + 3(2) + 3(3) = 3 + 6 + 9 = 18$$
- $$\sum_{r=1}^3 4 = 4 + 4 + 4 = 12$$
5. Add the results:
$$18 + 12 = 30$$
6. Calculate $$\sum_{r=1}^3 (3r + 4)$$ directly as a check:
$$3(1) + 4 + 3(2) + 4 + 3(3) + 4 = (3 + 4) + (6 + 4) + (9 + 4) = 7 + 10 + 13 = 30$$
7. Both methods give the same result, so the first statement is correct.
8. Next, verify the second summation:
$$\sum_{r=1}^4 (4r) = 4\sum_{r=1}^4 r$$
9. Calculate each side:
- Left side: $$4(1) + 4(2) + 4(3) + 4(4) = 4 + 8 + 12 + 16 = 40$$
- Right side: $$4 \times (1 + 2 + 3 + 4) = 4 \times 10 = 40$$
10. Both sides equal 40, confirming the validity of the distributive property in summation.
Final conclusion: Both summation expressions are correct as shown by evaluating and comparing both sides.