This week in precalc 12 we learned about adding and subtracting rational fractions.

To add or subtract rational expressions with unlike denominators, first find the LCM of the denominator. The LCM of the denominators of fraction or rational expressions is also called least common denominator , or LCD. Write each expression using the LCD. Make sure each term has the LCD as its denominator. Add or subtract the numerators. Simplify as needed.