## GMAT Quantitative Review

## 3.0 Math Review

### 3.2 Algebra

### 2. Equations

A major focus of algebra is to solve equations involving algebraic expressions. Some examples of such equations are

The *solutions* of an equation with one or more unknowns are those values that make the equation true, or “satisfy the equation,” when they are substituted for the unknowns of the equation. An equation may have no solution or one or more solutions. If two or more equations are to be solved together, the solutions must satisfy all the equations simultaneously.

Two equations having the same solution(s) are *equivalent equations*. For example, the equations

each have the unique solution . Note that the second equation is the first equation multiplied by 2. Similarly, the equations

have the same solutions, although in this case each equation has infinitely many solutions. If any value is assigned to *x*, then is a corresponding value for *y* that will satisfy both equations; for example, and is a solution to both equations, as is and .