Answer :
Problem:
solve -3/7 + -3/4
Solution:
Consider
[tex]-\frac{3}{7}+-\text{ }\frac{3}{4}[/tex]
our goal is to have the same denominator so we do the following trick:
[tex]-\frac{3}{7}+-\text{ }\frac{3}{4}\text{ = (}-\frac{3}{7}\text{x }\frac{4}{4})\text{ + (}-\frac{3}{4}\text{x }\frac{7}{7})[/tex]Notice that we multiply the numerator and denominator of one fraction by a fraction that contains the denominator of the other fraction in the equation. Now, the above equation is equivalent to:
[tex]-\frac{3}{7}+-\text{ }\frac{3}{4}\text{ = (}-\frac{3}{7}\text{x }\frac{4}{4})\text{ + (}-\frac{3}{4}\text{x }\frac{7}{7})\text{ = }-\frac{3(4)}{(7)(4)}\text{ }-\frac{3(7)}{(4)(7)}[/tex]that is:
[tex]-\frac{3}{7}+-\text{ }\frac{3}{4}\text{ = (}-\frac{3}{7}\text{x }\frac{4}{4})\text{ + (}-\frac{3}{4}\text{x }\frac{7}{7})\text{ = }-\frac{3(4)}{(7)(4)}\text{ }-\frac{3(7)}{(4)(7)}[/tex]