SOLUTION: how do i find the value of r in this equation. A line passes through the point r,5 and -2,r and has a slope of -2/9

Algebra ->  Inequalities -> SOLUTION: how do i find the value of r in this equation. A line passes through the point r,5 and -2,r and has a slope of -2/9       Log On


   

Question 1127854: how do i find the value of r in this equation.
A line passes through the point r,5 and -2,r and has a slope of -2/9
Answer by ikleyn(52765) About Me  (Show Source):
You can put this solution on YOUR website!
.
According to the definition of the slope, it is


    m = %28r-5%29%2F%28-2-r%29,


which gives you an equation


    %28r-5%29%2F%28-2-r%29 = -2%2F9,


or, equivalently,


    %28r-5%29%2F%282%2Br%29 = 2%2F9.


Solve it for "r".


    9*(r-5) = 2*(2+r)

    9r - 45 = 4 + 2r

    9r - 2r = 4 + 45

    7r = 49    ====>  r = 49/7 = 7.     ANSWER

Solved.