(1)
the equation of a line in slope-intercept form is
y = mx + c ( m is the slope and c the y-intercept )
y = - 3x + 4 is in this form with slope m = - 3
• Parallel lines have equal slopes, thus
y = - 3x + c ← is the partial equation
To find c substitute (- 3, - 7 ) into the partial equation
- 7 = 9 + c ⇒ c = - 7 - 9 = - 16
y = - 3x - 16 ← equation of line
(2)
rearrange 4x + 2y = 10 into slope- intercept form
subtract 4x from both sides
2y = - 4x + 10 ( divide all terms by 2 )
y = - 2x + 5 ← in slope- intercept form with m = - 2
y = - 2x + c ← partial equation
to find c substitute (4, 6 ) into the partial equation
6 = - 8 + c ⇒ c = 6 + 8 = 14
y = - 2x + 14 ← equation of line