Answer:
$142.95
Step-by-step explanation:
Given Original value of the sofa = $349
Rate of depreciation each year = 20%
Number of years = 4
To find the value of the sofa after 4 years use depreciation formula:
If the constant decrease in population be R% per annum. Then the population after n years is 

= 142.9504
= 142.95 (Nearest cent)
Hence, the value of sofa after 4 years is $142.95.
Answer:
No; the slopes of segment EF and segment DF are not opposite reciprocals.
Step-by-step explanation:
The slope between two points O(e, f) and X (g,h) is given as:

The slopes of segment EF and segment DF are given below:

For triangle DEF to be a right triangle, DF and EF are supposed to be perpendicular to each other. Two line are said to be perpendicular if the product of their slope is -1, i.e the slope of one line is the negative reciprocal (opposite reciprocal) of the other line.
Since the slope of DF and EF are not opposite reciprocals, ΔDEF is not a right triangle.
Answer:
yes
Step-by-step explanation: