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Aug 3, 2024
 #1
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For the first problem:

 

To address the problem, we will use the properties of similar triangles since lines DE and EF are parallel to sides BC and CD of triangle ABC.

Since DE is parallel to BC and EF is parallel to CD, triangle ADF is similar to triangle ABC.
The sides of similar triangles are proportional, so we can set up the following proportions:

ADAB=AFAC=DFBC

We know that AF=7 and DF=2. Let BD=x. The entire length AB can be expressed as:

AB=AD+DF=AD+2

Let’s designate AD=x. Hence, we have AB=x+2.

Considering the structure of triangle ADF in relation to triangle ABC, we also need to calculate AC in terms of AE:

Since EF is parallel to CD, triangles AEF and ACD are also similar, resulting in the relationship:

AEAC=AFAB=DFDC

But for our immediate task of determining the length BD just using AF and DF, we will not utilize this second proportion at the moment.

As both triangles ADF and ABC are similar due to the parallel lines, we can set the ratios of the line segments as follows:

ADAB=AFAC

But we know AB=AD+DF, substituting this gives us:

xx+2=77+2=79

Cross-multiplying yields:

9x=7(x+2)

Expanding the right-hand side:

9x=7x+14

Subtract 7x from both sides:

2x=14

Solving for x:

x=142=7

Thus, we find that AD=7.

Since we established BD=DF=2, thus:

BD=72=5

So the length of BD is:

5

Aug 3, 2024
Aug 2, 2024

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