Question

The two lines y=2/5x+9 and y=-2/5x-9 are: Parallel? Perpendicular? Or neither?

Answer 1

neither

Explanation:

in order for two lines to be parallel their slopes need to be the same. Both of these equations are written in slope intercept form which reveals the slope as the coefficient of x (the number in front of x). These coefficients are not the same so not parallel.

to be perpendicular the slopes need to be opposite reciprocals. For example, 3 and -1/3 or -5/8 and 8/5. These slopes are opposites since one is negative and one positive but they are not reciprocals so therefore not perpendicular

Answer 2

neither

Explanation:

if they were parallel, they would share the same gradient.

if a line were to be perpendicular to 2/5, the gradient would be -5/2 (the numerator and the denominator flips. if it is positive it'll change to negative, and if it's negative it'll become positive).

you don't need to look at the y-intercept, just focus on the gradient.

hope this helps!!