Question 271345
<font face="Garamond" size="+2">

5 and 4 have no factors in common so the LCD is just the product, namely 20.  Therefore:

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{4}{5}\ +\ \left(-\frac{3}{4}\right)]

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{16}{20}\ +\ \left(-\frac{15}{20}\right)]

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \frac{-16\,+\,\left(-15\right)}{20}]

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{31}{20}]

All of which makes good sense because:

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{4}{5}\ =\ -0.80]

and

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{3}{4}\ =\ -0.75]

and

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -0.80\ +\ (-0.75)\ =\ -1.55]

and

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -\frac{31}{20}\ =\ -1.55]

John
*[tex \LARGE e^{i\pi} + 1 = 0]
</font>