Diophantine Equations
1. **Problem:** Find the general integral solutions of the Diophantine equation $$5x + 8y = 1$$.
2. **Step 1:** Check if the equation has any integer solutions by verifying that $$ ext{gcd}(5,8)\mid 1$$.
Since $$\text{gcd}(5,8) = 1$$ and 1 divides 1, solutions exist.
3. **Step 2:** Use the Extended Euclidean Algorithm to find one particular solution for $$5x + 8y = 1$$.
- Divide 8 by 5: $$8 = 5 \times 1 + 3$$.
- Divide 5 by 3: $$5 = 3 \times 1 + 2$$.
- Divide 3 by 2: $$3 = 2 \times 1 + 1$$.
- Since the remainder is 1, back substitute to express 1 as a combination of 5 and 8:
$$1 = 3 - 2 \times 1$$
But $$2 = 5 - 3 \times 1$$, so:
$$1 = 3 - (5 - 3 \times 1) = 2 \times 3 - 5$$
Also, $$3 = 8 - 5 \times 1$$, so:
$$1 = 2 \times (8 - 5) - 5 = 2 \times 8 - 3 \times 5$$
4. **Step 3:** The particular solution is $$x_0 = -3, y_0 = 2$$.
5. **Step 4:** The general solution for the equation $$5x + 8y = 1$$ is given by:
$$x = x_0 + \frac{8}{1}t = -3 + 8t$$
$$y = y_0 - \frac{5}{1}t = 2 - 5t$$
where $$t$$ is any integer.
6. **Problem:** Find the general integral solutions of the Diophantine equation $$19x + 11y = 4$$.
7. **Step 1:** Check if solutions exist by verifying $$\text{gcd}(19,11)\mid 4$$.
Since $$\text{gcd}(19,11) = 1$$ and 1 divides 4, solutions exist.
8. **Step 2:** Use Extended Euclidean Algorithm to find one particular solution for $$19x + 11y = 1$$:
- $$19 = 11 \times 1 + 8$$
- $$11 = 8 \times 1 + 3$$
- $$8 = 3 \times 2 + 2$$
- $$3 = 2 \times 1 + 1$$
- Back substitute:
$$1 = 3 - 2 \times 1$$
$$2 = 8 - 3 \times 2$$
Substitute back:
$$1 = 3 - (8 - 3 \times 2) = 3 \times 3 - 8$$
$$3 = 11 - 8$$, so
$$1 = (11 - 8) \times 3 - 8 = 3 \times 11 - 4 \times 8$$
$$8 = 19 - 11$$, so
$$1 = 3 \times 11 - 4 \times (19 - 11) = 7 \times 11 - 4 \times 19$$
9. **Step 3:** The particular solution for $$19x + 11y = 1$$ is $$x_0 = -4, y_0 = 7$$.
10. **Step 4:** Multiply the particular solution by 4 to find solution for $$19x + 11y = 4$$:
$$x = -4 \times 4 = -16$$
$$y = 7 \times 4 = 28$$
11. **Step 5:** The general solution for $$19x + 11y = 4$$ is:
$$x = -16 + 11t$$
$$y = 28 - 19t$$
where $$t$$ is any integer.
**Final answers:**
- For $$5x + 8y = 1$$:
$$x = -3 + 8t$$
$$y = 2 - 5t$$
- For $$19x + 11y = 4$$:
$$x = -16 + 11t$$
$$y = 28 - 19t$$
where $$t\in \mathbb{Z}$$.