One concept that is essential for ACT Math (I put it into the category of what I call ACT Math "Have to Know") is the slope-intercept form of a line, or y=mx+b.

Now, memorizing this formula isn't enough. Instead, students must come to understand the multitude of questions associated with this formula and its meaning that are necessary for most ACT math tests. You may not be asked all of the following, but you will definitely need slope-intercept form for every ACT math test regarding at least 1 (if not more!) of the following topics:

a) Simply putting a line in another form (such as 5x - 2y = 8) into slope-intercept form.

b) Knowing what the y-intercept is (where the line, when graphed, crosses the y-axis). In the equation, this is "b".

c) Finding the slope of a line (which requires putting it into slope-intercept form by solving for y, then identifying "m").

d) Finding the slope of a line parallel to one you're given (simple enough: they will have the same slope, or m).

e) Finding the slope of a line perpendicular to one you're given (take the negative reciprocal of m, which requires making it negative and then flipping the numerator and denominator).

f) Identify a point that a line passes through (can be found by plugging in points for x and y and finding which point "satisfies" the equation).

If any of this sounds fuzzy, don't worry: I explain it all on my __YouTube channel here__.

Want some ACT cheat sheets to help out? __Click here to download__ for free!

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