# Quadratic Equations

A quadratic equation is any expression of the form:

**ax ^{2} + bx + c = 0, a ≠ 0.**

### Solving Quadratic Equations

To solve quadratic equations use the following formula:

**If a<0, multiply two members by (−1).**

## Incomplete Quadratic Equations

A quadratic equation is incomplete if any of its coefficients: b or c, or both, are zero.

### Solving Incomplete Quadratic Equations

### ax^{2} = 0

The solution is x = 0.

### ax^{2} + bx = 0

Remove the common factor, x:

The 1st factor equals 0.

A solution is always x = 0.

The other solution was obtained by solving the linear equation resulting from equating the 2nd factor to zero.

### ax^{2} + c = 0

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