1. **State the problem:** We are given the sequence $1, 3, 4, 7, 11, \ldots$ and need to find a recursive rule for it and then write the next two terms.
2. **Analyze the sequence:** The first two terms are given as $a_1 = 1$ and $a_2 = 3$.
3. **Find the recursive rule:** Look at how terms relate to previous terms.
Calculate differences:
$$3 - 1 = 2$$
$$4 - 3 = 1$$
$$7 - 4 = 3$$
$$11 - 7 = 4$$
Notice the pattern in differences resembles the sequence itself shifted.
Try the recursive formula:
$$a_n = a_{n-1} + a_{n-2}$$
Check for $n=3$:
$$a_3 = a_2 + a_1 = 3 + 1 = 4$$ (matches)
Check for $n=4$:
$$a_4 = a_3 + a_2 = 4 + 3 = 7$$ (matches)
Check for $n=5$:
$$a_5 = a_4 + a_3 = 7 + 4 = 11$$ (matches)
4. **Write the recursive rule:**
$$a_1 = 1, \quad a_2 = 3, \quad a_n = a_{n-1} + a_{n-2} \text{ for } n \geq 3$$
5. **Find the next two terms:**
$$a_6 = a_5 + a_4 = 11 + 7 = 18$$
$$a_7 = a_6 + a_5 = 18 + 11 = 29$$
**Final answer:**
Recursive rule: $a_1 = 1$, $a_2 = 3$, $a_n = a_{n-1} + a_{n-2}$ for $n \geq 3$
Next two terms: $18$ and $29$
Recursive Sequence D4Ff6C
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.