Equation of a line in slope-intercept form

Write an equation of a line, in slope-intercept form, which passes through points (4,6) and (6,12)

(4,6) , (6,12)

y2 - y1
--------- = slope
x2 - x1

12 - 6
--------   {substituted coordinates into slope formula}
6 - 4

6
---   {subtracted on top and bottom}
2

slope = 3   {divided 6 by 2}

Point-slope formula is:
y - y1 = m(x - x1)  {m is the slope and (x1,y1) are the coordinates of the point}

(4,6), m = 3
y - 6 = 3(x - 4)   {substituted slope and first point into point-slope formula}
y - 6 = 3x - 12   {used distributive property}
y = 3x - 6   {added 6 to both sides}

Ask Algebra House