Question 105047
Let's use the slope-intercept form because these equations are in that form.

{{{y=mx+b}}}

NOTE:Lines are parallel if and only if their slopes are equal.


In this form, m is the slope.

So, we will find a pair with the same slope.


a)m=9
b)m=-9
c)m=9
d)m=1


Thus, a) and c) are parallel. Wanna see some proof? Look below!


{{{graph(700,700,-10,10,-10,10,9x-7,9x+3)}}}



Power up,
HyperBrain!