Are the lines y = –x – 4 and 5x + 5y = 20 perpendicular? explain.

Comments (7) on “Are the lines y = –x – 4 and 5x + 5y = 20 perpendicular? explain.”

1. In second equation, 5x + 5y = 20
   5y = -5x + 20
   Divide the equation by 5, 
   y = -x + 4
   Here, Slope = -1

   Perpendicular line must have slope equal to 1 [ which is opposite & reciprocal ]
   But in y = -x - 4, slope = -1 so they are not perpendicular.

   In short, Your Answer would be Option D) No, their slopes are not opposite reciprocals.

   Hope this helps!

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2. No. they are parallel bc when u turn tge standard form to slope intercept form it is. the same slope diferent intercept

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3. The lines consider perpendicular if (the slope of line 1) * (the slope of line 2) = -1 
   so get the slope of the lines ,1st put the equation on the form of y = mx+c 
   where the coefficient of x (m) is the slope
   y=-x-4 m1= -1
   5x+5y=20
   y=-x+4 m2 = -1
   so m1 * m2 = -1 * -1 = 1
   then, the two lines aren't perpendicular  

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4. No the slopes are not equal. 

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5. Y=mx+b
   m=slope

   ax+by=c
   -a/b=slope

   if slopes muliply to -1 then they are perpendicular

   given

   y=-1x-4
   slope is -1

   5x+5y=20
   slope=-5/5=-1

   -1 timesm -1=1≠-1
   not perpendicular

   D is answer

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6. Actually no, they are not perpendicular because they both have a negative slope. We know this when we plot points (x,y) to see y= -x-4 5x+5y=20
   Please give it a check by this sucession of numbers
   ( -1, -3 ) (-1, 5 ) 
   ( 0, -4 ) ( 0, 4 ) 
   ( 1, -5 ) ( 1, 3 ) 
   ( 2, -6 ) ( 2, 2 ) 
   ( 3, -7 ) ( 3, 1 ) 
   ( 4, 8 ) ( 4, 0 ) 
   ( 5, -9 ) ( 5, -1 ) 
   I hope this helped you

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7. No. they are parallel bc when u turn tge standard form to slope intercept form it is. the same slope diferent intercept

   Reply