x - 4y = 15
-x -x (subtract x on both sides)
-4y = 15 -x
---- -------- (divide by -4 on both sides)
-4 -4
y = -3.75 - 1/4x (change to slope-intercept form which will be y = -1/4x -3.75)
substitute that equation for y on the other equation so you will get
x - 4(-1/4x - 3.75) = 15
x + 1x + 15 = 15 (use distributive property)
2x + 15 = 15 (combine like terms)
2x = 0 (subtract 15 on both sides)
x = 0 (divide both sides by 2)
substitute for x on any equation (Im going to be using x - 4y = 15)
0 - 4y = 15
-4y = 15 (add 0 to both sides)
y = -3.75 (divide both sides by -4)
Point of intersection is (0, -3.75)
