Question

A line passes through (1,-1) and (3,5) . What is the equation of the line in slope-intercept form?

A.) Y = x-2
B.) Y = 3x-5
C.) Y = 3x-4
D.) Y = 2x-3

Answer 1

(1,-1) and (3,5)

Find slope first

y=mx+b

slope is also m

b is y-intercept

slope = y2-y1/x2-x1

x1=1

x2=3

y1=-1

y2=5

5-(-1)/(3)-(1)

6/2=3

y=3x+b

use (1,-1) into y=3x+b ( using substitution method)

-1=3(1)+b

-1=3+b

Move 3 to the other side

Sign changes from +3 to -3

-1-3+3-3+b

b=-4

Answer: C.) Y = 3x-4