Point-slope form is y − y1 = m(x − x1). You need one point and the slope. You do not need the intercept yet. Slope is in slope on ACT Math.
Plug the point in
A line with slope 3 through (2, 5) is y − 5 = 3(x − 2). Distribute only if the choices are in slope-intercept form. Then y = 3x − 1. If the choices already look like y − y1 = m(x − x1), leave it.
Converting to y = mx + b is in slope-intercept form. A line parallel to this one keeps m = 3 and uses a different point. That rule is in parallel and perpendicular lines.
The bottom line
Subtract the known y, multiply the slope by (x minus the known x). Convert to y = mx + b only if the answers are written that way. The plane these lines live on is in coordinate geometry.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
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