**7.1 Algebraic Formulae**

7.1.1 Variables and Constant

7.1.1 Variables and Constant

**1.**A variable is a quantity without a fixed value.

**2.**A constant is a quantity with a fixed value.

**7.1.2 Concept of Formulae**

**1.**An algebraic formula is an equation which shows the

**relationship**between several variables and/ or constant.

**2.**The subject of an algebraic formula is a

**linear variable**expressed in terms of the other variables.

*Example 1:*
$\text{Express}x\text{intermsof}y\text{,if}y=\frac{2-3x}{x}.$

Solution:Solution:

$\begin{array}{l}y=\frac{2-3x}{x}\\ xy=2-3x\\ xy+3x=2\\ x\left(y+3\right)=2\\ x=\frac{2}{y+3}\end{array}$

Example 2:Example 2:

$\text{Giventhat}s=\frac{{p}^{2}-{q}^{2}}{2u}\text{,make}p\text{thesubjectoftheformula}\text{.}$

Solution:Solution:

$\begin{array}{l}s=\frac{{p}^{2}-{q}^{2}}{2r}\\ 2rs={p}^{2}-{q}^{2}\\ {p}^{2}=2rs+{q}^{2}\\ p=\sqrt{2rs+{q}^{2}}\end{array}$