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# Simultaneous Linear Equations of Two Variables

## 7.1 Simultaneous Linear Equations of Two Variables

#### Geometry of Simultaneous Linear Equations

• Suppose you are asked to solve the simultaneous equations \begin{cases}x-y=2 \\2 x+3 y=10\end{cases}. In fact, each equation represents a line, if drawn on a 2-D coordinate plane.
• Thus, solving the simultaneous equations is similar to finding the intersection point of two lines.
• Consider solving two simultaneous equations for two unknowns. Interpreting geometrically, we want to find the intersection point(s) of two lines. There are three possible scenarios:
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## 6.4 Systems with a Single Parameter

### System of Equations with a Single Parameter

• We have seen how simultaneous equations look like. For instance,

\left\{\begin{array}{ll}6=x+y+z & (1) \\ 4=4 x+2 y+z & (2)\end{array}\right.

and how there can be unique, infinite or no solutions for each set of simultaneous equations. These are explored in section “Solving Simultaneous Linear Equations” in A2 – Algebra.

• Literal equations are very similar, just that instead of just numbers, we will have unknown constants. Such as,

\left\{\begin{array}{ll}x+y=2 m+3 & (1) \\ 3 x-2 y=7 m-1 & (2)\end{array}\right.

where m is a constant. Hence the solution (x,\ y) will be expressed in terms of m, and again there are unique, infinite, or no solutions. This will depend on the value(s) of m.

• Parameters are a little different from literals. They are technically speaking, variables and not constants. It can be seen as a link between two (or more) variables.
• For instance, take a cuboid with side length x for example. We denote the surface area as S, volume as V, then we have
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