Answer:
The lines DE and BC have the same slope, therefore the two lines, DE and BC, are parallel
Step-by-step explanation:
To prove that DE is parallel to BC, we have;
The slope, m of the lines DE and BC are found from the following equation;

Where;
(x₁, y₁) and (x₂, y₂) = (b, c) and (a + b + c) for DE, we have;

Where we have (x₁, y₁) and (x₂, y₂) = (0, 0) and (2a, 0) for BC, we have;

Therefore, because the lines DE and BC have the same slope, the two lines DE and BC are parallel.
Answer:
<h2>3</h2>
Step-by-step explanation:
IF point E lies on the line segment DF, this means that all the points DEF are collinear and DE+EF = DF.
Given parameter
DE = 6
DF = 9
Required
EF
Substituting the given parameter into the expression above to get the required will be;
DE+EF = DF.
EF = DF-DE
EF = 9-6
EF = 3
Hence the length of EF is equivalent to 3

the -7 is found there twice, so it has a multiplicity of 2
the +7 is there thrice, so it has multiplicity of 3