system of equations

Question

Use a system of equations to find the equation of a line, in slope-intercept form, that contains the given points, (-negative2, 1) and (8,-negative1). 

Answer 1

Slope-intercept form looks like:    y=mx+b

 

To use a system of equations:

Eq. 1:   1 = m(-2) + b

Eq. 2:   -1 = m(8) + b

 

Using elimination method, subtract equations:

     1   =   -2m   +   b      [Eq1]

    -1    =   8m   +  b      [Eq2]

  ----------------------

      2   = -10m

      -1/5 = m

 

Substitution into Eq1:

    1 = (-1/5)(-2) + b

    1 = 2/5 + b

    3/5 = b

 

The equation is:

    y = -x/5 + 3/5

Answer 2

Hy Barbara,

 

The two points we are given are (-2,1) and (8,-1).

 

 

Slope = ( -1 - 1) / ( 8 + 2)

 

= -2 / 10

 

= -1/5

 

The equation of the line in slope intercept form

 

y -1 = -1/5 (x + 2)

 

y = -x/5 -2/5 + 1

 

y = -x/5 + 3/5