179,169 views
16 votes
16 votes
Determine if the lines are parallel, perpendicular, neither or the same line: y = -2x + 1 and -2x + 4y = 5.

User Ryan Gibbs
by
2.7k points

2 Answers

22 votes
22 votes
They are perpendicular
User Donshikin
by
3.1k points
11 votes
11 votes

Answer: These lines are perpendicular

Explanation:

Let's use slope intercept form, y=mx+b (m=slope, b=y intercept)

Parallel lines have the same slope, or m

  • y=3x+7 and y=3x+32 are parallel because they have the same m

Perpendicular lines have an opposite reciprocal slope

  • y=2x+13 and y= -1/2+2 are perpendicular because they are reciprocals

y=-2x+1 is already in slope intercept form. Let's change the other problem

  1. -2x+4y=5
  2. isolate the y, 4y=2x+5
  3. make y by itself, y=2/4x+5/4 or y=1/2x+5/4

Here are the two problems: y=-2x+1 and y=1/2x+5/4

Look closer. These lines are actually perpendicular.

Take the second problem's slope, 1/2. Make it a negative reciprocal, which means -2/1 or -2. These lines are perpendicular.

User Nika Roffy
by
2.8k points