Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
7. Writing Equations in Point-Slope Form
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Exercise 27 Page 184

What do parallel lines have in common?

y=4x-30

Practice makes perfect

Consider the given equation of a line. y= 4x-3 When lines are parallel, they have the same slope. Because of this, we know that all lines that are parallel to the line whose equation is given will have a slope of 4. We can write a general equation in slope-intercept form for these lines. y= 4x+ b We are asked to write the equation of a line parallel to the given equation that passes through the point ( 8, 2). By substituting this point into the above equation for x and y, we will be able to solve for the y-intercept b of the parallel line.

y=4x+b
2=4( 8)+b
â–¼
Solve for b
2=32+b
2-32=32+b-32
-30=b
b=-30

Now that we have the y-intercept, we can write the parallel line to y=4x-3 through (8,2). y = & 4x+( -30) & ⇕ y= & 4x-30