# Algebra – Core Concepts (JEE Level)

## Linear Equations
ax + b = 0  
Solution: x = −b / a, where a ≠ 0

## Quadratic Expressions
Standard form: ax² + bx + c

## Identities
(a + b)² = a² + 2ab + b²  
(a − b)² = a² − 2ab + b²  
a² − b² = (a − b)(a + b)

## Inequalities
- Multiplying/dividing by a negative reverses the sign
- Check solution intervals carefully

## Common Mistakes
- Cancelling terms incorrectly
- Ignoring restrictions on variables