Exercise · ZW-LINEAR-CONGRUENCE-007 · ★★☆ Intermediate
Solve \(5x \equiv 4 \pmod{9}\). What is the solution modulo 9?
Choose one option.
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- A. 8
Explanation
Since \(5\cdot 2=10\equiv 1\pmod{9}\), the inverse of 5 is 2, so \(x\equiv 8\pmod{9}\).
Review the concept: Linear congruence
A linear congruence is a first-degree congruence in one unknown \(x\), with integer coefficients \(a\), \(b\) and modulus \(m\); its solutions are the integers \(x\) that satisfy it.
\[ax \equiv b \pmod{m}\]
More practice problems: linear congruence
- ZW-LINEAR-CONGRUENCE-001 What is the modular inverse of 3 modulo 7?
- ZW-LINEAR-CONGRUENCE-002 What is the greatest common divisor of 4 and 6?
- ZW-LINEAR-CONGRUENCE-003 How many solutions modulo 10 does the congruence 3x ≡ 1 pmod10 have?
- ZW-LINEAR-CONGRUENCE-004 Does the congruence 2x ≡ 1 pmod4 have a solution?
- ZW-LINEAR-CONGRUENCE-005 What is the value of x in x ≡ 3 pmod5 that lies between 0 and 4?
- ZW-LINEAR-CONGRUENCE-006 Solve 3x ≡ 2 pmod7. What is the solution modulo 7?
- ZW-LINEAR-CONGRUENCE-008 Solve 2x ≡ 4 pmod6. How many solutions modulo 6 does it have?
- ZW-LINEAR-CONGRUENCE-009 Solve 4x ≡ 2 pmod10. What is the set of solutions modulo 10?