1. S2B Chapter 9 Algebraic Fractions and Formulae

2. 2009 Chung Tai Educational Press. All rights reserved. © Algebraic Fractions If P and Q are polynomials, where Q involves variables and Q  0, then the expression is known as an algebraic fraction. e.g. and are algebraic fractions but and are not algebraic fractions 2 5  x

3. 2009 Chung Tai Educational Press. All rights reserved. © Multiplication and Division of Algebraic Fractions The multiplication and division of algebraic fractions are similar to those of fractions. Before performing the operations of multiplication or division, we should factorize the numerator and denominator first, and then cancel out the common factors. For example:

4. 2009 Chung Tai Educational Press. All rights reserved. © Addition and Subtraction of Algebraic Fractions The addition and subtraction of algebraic fractions are similar to those of fractions. When the denominators in algebraic fractions are different, we need to convert them into a common denominator before the addition or subtraction of their numerators. For example:

5. 2009 Chung Tai Educational Press. All rights reserved. © Formulae Formula is an algebraic equality to express the relation among variables.

6. 2009 Chung Tai Educational Press. All rights reserved. © Some Common Formulae in Mathematics Formula of area of rectangle: A  b  l where A, b and l represent area, width and length respectively. Formula of area of trapezium: where A, a, b and h represent area, length of upper base, length of lower base and height respectively....

7. 2009 Chung Tai Educational Press. All rights reserved. © Substitution The process of replacing variables in a formula by some values is called substitution. For example: 10  14  F  2 F  6 For V  E  F  2, when V  10 and E  14,

8. 2009 Chung Tai Educational Press. All rights reserved. © Subject of a Formula In the formula V  E  F  2, V is called the subject of the formula. In a formula, when a variable is expressed in terms of other variables, it is called the subject of the formula.

9. 2009 Chung Tai Educational Press. All rights reserved. © Change of Subject of a Formula The following formulae can be interchanged with each other with different subjects. E  V  F  2V  E  F  2 V is the subject E is the subject Change of subject

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