Easy Algebra Step-by-Step

The Equation of a Line 193

Step 2. Now use the point-slope formula and one of the given points to fi nish

writing the equation. Let (x, y) be a point on the line different from,

say, (3, −7).

y

x

−()−

−

=−

3

11

4

Step 3. Solve the equation for y to get the slope-y-intercept form of the

equation.

y

x

−()−

−

=−

3

11

4

yx+ (^7) ()xx−

11

4

yx+ 7 −+x

11

4

33

4

yx+ 77 +−

11

4

33

4

7

yx+−

11

4

33

4

28

4

yx+

11

4

5

4

is the equation of the line.

Exercise 18

1. Given the slope m= 4 and the y-intercept y= 3, write the equation of the
   line.


2. Given the slope m = −3 and the y-intercept y = −3, write the equation of
   the line.


3. Given the slope m=

1

3 and the y-intercept y= 0, write the equation of the

line.

4. Given the slope m = 2 and a point (1, 1) on the line, write the equation of
   the line.


5. Given the slope m= −1 and a point (2, 3) on the line, write the equation
   of the line.

When two points are known, it

does not make any difference

which one is chosen to fi nish

writing the equation.