Solve Congruence
1. **State the problem:** Solve the congruence equation $$2x - 1 \equiv 2 \pmod{5}$$.
2. **Rewrite the equation:** Add 1 to both sides to isolate the term with $x$:
$$2x - 1 + 1 \equiv 2 + 1 \pmod{5}$$
which simplifies to
$$2x \equiv 3 \pmod{5}$$.
3. **Understand the goal:** We want to find an integer $x$ such that when $2x$ is divided by 5, the remainder is 3.
4. **Find the multiplicative inverse of 2 modulo 5:** Since 5 is prime, the inverse of 2 modulo 5 exists. We look for a number $k$ such that
$$2k \equiv 1 \pmod{5}$$.
Testing values:
- $2 \times 3 = 6 \equiv 1 \pmod{5}$
So, the inverse of 2 modulo 5 is 3.
5. **Multiply both sides of the congruence by 3:**
$$3 \times 2x \equiv 3 \times 3 \pmod{5}$$
which simplifies to
$$6x \equiv 9 \pmod{5}$$.
6. **Reduce coefficients modulo 5:**
$$6x \equiv 9 \pmod{5}$$ becomes
$$1x \equiv 4 \pmod{5}$$
since $6 \equiv 1 \pmod{5}$ and $9 \equiv 4 \pmod{5}$.
7. **Final solution:**
$$x \equiv 4 \pmod{5}$$
which means $x$ can be any integer of the form
$$x = 4 + 5k$$
for any integer $k$.
**Answer:** The solution to the congruence is $$x \equiv 4 \pmod{5}$$.