Week 14 – Pre Calculus 11

In this week of pre calc we were working on rational expressions. We learned how we can simplify, multiply or divide, add or subtract them.

For multiplying or dividing we have the same rule. because we do the dividing question by converting them into a multiply question. the same thing that we do when we want to divide 2 fractions:

1/2 ÷ 2/6 =                                                                                                                                                         1/2 x 6/2 =                                                                                                                                                            6/4 = 3/2

For multiplying or dividing rational expressions we should pay attention to the non-premissible values. Non-premissible values are the numbers that makes the denominator of a fraction equal to zero. Those are the values that we shouldn’t put instead of our parameters.

After finding the non-premissible values we can use the same rules as we use for the frictions. We can cancel out the common thing from numerator and denominator and then simplify them.

Example1:

4x/6 . 12/2x² =

x≠0

2/1 . 2/x =

4/x. ,  x≠0

Example 2:

3x²/16 ÷ 9x/48 =

x≠0

3x²/16 . 48/9x =

x/1 . 3/3 = 3x/3 =

x. ,  x≠0

Example 3:

3x/25y² ÷ 6/5y(x²-4) . 1/(x-2)=

x≠ ±2 , y≠0

3x/25y² . 5y(x²-4)/6 . 1/(x-2)=

3x/25y² . 5y(x-2)(x+2)/6 . 1/(x-2)=

x/5y . (x+2)/2 . 1/1=

x(x+2)/10y  ,  x≠ ±2 & y≠0

 

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