Algebraic Fractions

When adding or subtracting algebraic fractions, the first thing to do is to put them onto a common denominator (by cross multiplying).

e.g.      1      +      4    
(x + 1)       (x + 6)

= 1(x + 6) + 4(x + 1)
(x + 1)(x + 6)

= x + 6 + 4x + 4
(x + 1)(x + 6)

=    5x + 10    
(x + 1)(x + 6)

 

Solving equations
When solving equations containing algebraic fractions, first multiply both sides by a number/expression which removes the fractions.

Example:
Solve    10    –   2   =  1
(x + 3)     x

multiply both sides by x(x + 3):
\ 10x(x + 3)2x(x + 3) = x(x + 3)
(x + 3)            x

\ 10x – 2(x + 3) = x² + 3x      [after cancelling)
\ 10x – 2x – 6 = x² + 3x
\ x² – 5x + 6 = 0
\ (x – 3)(x – 2) = 0
\ either x = 3 or x = 2