Y-y1=a(x-x1)
a=(y2-y1)/(x2-x1)
a= (6-(-2))/(7-1)
a=8/6
a=4/3
y-6=4/3(x-7)
y-6=4/3x-28/3
y=4/3x-28/3+6
y=4/3x-10/3 >>ef
The value of the missing length is 20
Let the missing length be x
From Parallel lines and transversal theorem, we have that
If three or more parallel lines intersect two transversals, then they cut off the transversals proportionally.
Then, we can write that

∴ 
x = 20
Hence, the value of the missing length is 20
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Making the assumption that your problem looks like this,

we use the distributive property to multiply:
the equation in the slope-intercept of the side of triangle ABC that is perpendicular to segment EF is y = x + 1
<h3>How to determine the equation</h3>
From the figure given, we can deduce the coordinates of the sides
For A
A ( 4,2)
For B
B ( 4, 5)
C ( 1, 2)
D ( 2, -4 )
E ( 5, -4)
F ( 2, -1)
The slope for BC
Slope = 
Substitute the values for both B and C coordinates, we have
Slope = 
Find the difference for both the numerator and denominator
Slope = 
Slope = 1
We have the rotation for both point ( 0, 1)
y - y1 = m ( x - x1)
The values for y1 and x1 are 1 and 0 respectively and the slope m is 1
Substitute the values
y - 1 = 1 ( x - 0)
y - 1 = x
Make 'y' the subject of formula
y = x + 1
Thus, the equation in the slope-intercept of the side of triangle ABC that is perpendicular to segment EF is y = x + 1
Learn more about linear graphs here:
brainly.com/question/4074386
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