Math  /  Geometry

QuestionQuestion Show Ex
In the diagram below of triangle BCD,EB C D, E is the midpoint of BD\overline{B D} and FF is the midpoint of CD\overline{C D}. If EF=21+3xE F=-21+3 x, and BC=24+4xB C=-24+4 x, what is the measure of BC\overline{B C} ?

Studdy Solution

STEP 1

1. E E is the midpoint of BD\overline{BD}.
2. F F is the midpoint of CD\overline{CD}.
3. EF EF is a line segment connecting midpoints E E and F F .
4. EF=21+3x EF = -21 + 3x .
5. BC=24+4x BC = -24 + 4x .
6. We need to find the measure of BC\overline{BC}.

STEP 2

1. Use the Midsegment Theorem to relate EF EF and BC BC .
2. Set up an equation using the given expressions for EF EF and BC BC .
3. Solve for x x .
4. Substitute x x back into the expression for BC BC to find its measure.

STEP 3

According to the Midsegment Theorem, the segment connecting the midpoints of two sides of a triangle is parallel to the third side and half its length. Therefore, EF=12BC EF = \frac{1}{2} BC .

STEP 4

Using the Midsegment Theorem, set up the equation:
EF=12BC EF = \frac{1}{2} BC
Substitute the given expressions:
21+3x=12(24+4x) -21 + 3x = \frac{1}{2}(-24 + 4x)

STEP 5

Solve the equation for x x :
First, simplify the right side:
21+3x=12(24+4x) -21 + 3x = \frac{1}{2}(-24 + 4x) 21+3x=12+2x -21 + 3x = -12 + 2x
Now, solve for x x :
3x2x=12+21 3x - 2x = -12 + 21 x=9 x = 9

STEP 6

Substitute x=9 x = 9 back into the expression for BC BC :
BC=24+4x BC = -24 + 4x BC=24+4(9) BC = -24 + 4(9) BC=24+36 BC = -24 + 36 BC=12 BC = 12
The measure of BC\overline{BC} is:
12 \boxed{12}

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