Question

An equation of the line that contains the origin and the point (1,3) is

A) y=3x+1
B) y/3=x-1
C) y=3x
D) y=c-1
E) 3y=x

Answer 1

The general equation for a straight line is
y = mx + c
where
m = slope
c = y-intercept

The line passes through the origin (0,0), therefore
0 = m*0 + c => c = 0
Therefore the equation is of the form
y = mx

The line passes through (1,3). Therefore
3 = m*1 => m = 3.

The equation for the line is
y = 3x

Answer: C) y=3x