Question 320150
"Decide whether these lines are parallel, perpindicular or neither 
5x+2y=10
2x-5y=7 
I think that are perpendicular because they are opposites! 
Can you please help me? 
Thank you"

slope-intercept form of a line is y=mx+b, 
where m is the slope,
and b is the y-intercept (vertical-intercept or the point (0,b))

5x + 2y = 10
     2y = -5x + 10
      y = (-5/2)x + 5 --> m = -5/2, b = 5
2x - 5y = 7
   - 5y = -2x + 7
      y = (2/5)x - (7/5) --> m = 2/5, b = -7/5

they are perpendicular
since the 2 slopes are reciprocals and their product is -1