The most useful form of straight-line equations is the "slope-intercept" form:
y = mx + b
m is the slope and "b" gives the
y-intercept.
3x-5y=8
-5y=8-3x Divide with -5
y=(-8/5)+(3x/5)
y=(3/5)x-8/5
The other format for straight-line equations is called the "point-slope" form. For this one, they give you a point (x1, y1) and a slope m, and have you plug it into this formula:
y-y1= m(x – x1)
Parallel lines have same slope.
In this case:
m=3/5
x1=9
y1= -9
y-y1= m(x – x1)
y-(-9)=(3/5)*(x-9)
y+9=(3/5)x-(3*9/5)
y=(3/5)x-(27/5)-9
y=(3/5)x-(27/5)-(45/5)
y=(3/5)x-72/5
OR:
y-(3/5)x= -72/5 Multiply with -5
-5y+3x=72
3x-5y=72
y=(1/4)x-6
write an equation of the line containing the given point and parallel to the given line (9,-9); 3x-5y=8
1 answer