Rearrange all of them in terms of y:
6x - 2y = -7
y = (-6x -7)/-2
y = 3x + 7/2
1) - 2x + 6y = 2
y = 1/3x + 1/3
2) 3x - y = 5
y = 3x - 5
3) 8x - 2y = 7
y = 4x - 7/4
4) 9x - 3y = 8
y = 3x - 8/3
5) x + 3y = 12
y = -x/3 + 4
Parallel lines have equal gradients; the gradient is the coefficient of x.
2 and 4 are parallel to the original eq'n as they have 3x just like the original eq'n.
Perpendicular lines have gradients that are negative reciprocals of each other; they multiply to give -1.
5 is the only one perpendicular to the original as -x/3 * 3 = -1
1 and 3 are therefore neither.
