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# Graphing Problem

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What is the y-intercept form for the two points (0, -1) and (3,-2) if their relationship is proportional?

Oct 26, 2017

#1
+7348
+1

I think you want the slope-intercept form for the equation of a line that passes through these points.

slope intercept form is:     y = mx + b     , where  " m "  is the slope and  " b"  is the y-intercept.

slope  =  $$\frac{\text{change in y}}{\text{change in x}}\,=\,\frac{y_2-y_1}{x_2-x_1}\,=\,\frac{-2-(-1)}{3-0}\,=\,\frac{-2+1}{3}\,=\,-\frac13$$

→    m  =  - $$\frac13$$

Since  (0, -1)  is a point on the line, we know that when  x = 0 ,  y = -1  .   So...

the y-intercept  =  -1

→    b  =  -1

So our equation is

y  =  - $$\frac13$$x  - 1

Oct 26, 2017
edited by hectictar  Oct 26, 2017

#1
+7348
+1

I think you want the slope-intercept form for the equation of a line that passes through these points.

slope intercept form is:     y = mx + b     , where  " m "  is the slope and  " b"  is the y-intercept.

slope  =  $$\frac{\text{change in y}}{\text{change in x}}\,=\,\frac{y_2-y_1}{x_2-x_1}\,=\,\frac{-2-(-1)}{3-0}\,=\,\frac{-2+1}{3}\,=\,-\frac13$$

→    m  =  - $$\frac13$$

Since  (0, -1)  is a point on the line, we know that when  x = 0 ,  y = -1  .   So...

the y-intercept  =  -1

→    b  =  -1

So our equation is

y  =  - $$\frac13$$x  - 1

hectictar Oct 26, 2017
edited by hectictar  Oct 26, 2017