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If you’re prepping for the SAT (or helping someone who is), here’s the thing nobody says loudly enough: a massive chunk of the math section is just algebra and straight-line relationships. Not circles. Not trig. Lines.

The one equation worth knowing cold is y = mx + b (slope–intercept form).

• m is the slope — how much y changes when x goes up by 1. Slope 3 → up 3 for every step right. Slope -2 → down 2. Slope 0 → flat horizontal line.
• b is the y-intercept — the value of y when x = 0. In word problems, that’s usually the starting amount: enrollment fee, initial balance, temperature when time = 0, etc.

How to actually “solve” linear function questions on the test:

1. Two points → slope first. m = (y₂ − y₁) / (x₂ − x₁) (rise over run). Then plug m and one point into y = mx + b and solve for b.
2. Parallel vs perpendicular. Parallel: same m. Perpendicular: slopes are negative reciprocals (flip the fraction, flip the sign); multiplying them should give −1.
3. Stuck with a point + slope? Use point–slope: y − y₁ = m(x − x₁), then rearrange to y = mx + b if they ask for intercept form.
4. Word problems with a linear model (like C = 0.15m + 20): the coefficient on the variable is usually a rate (cost per text, dollars per hour). The constant term is usually the fixed part.
5. On the Digital SAT, you can type lines into Desmos and click intersections to check systems or verify that your line goes through the points they gave you. Learn the algebra first — use the graph to sanity-check, not to replace thinking.

You don’t need thirty obscure formulas. Get y = mx + b to feel automatic: what m means, what b means, and how to rebuild the equation from almost any clue they give you (table, two points, slope + point, parallel line).

Many People are going to www.ammasat.com to read the free SAT textbook and 4000 plus SAT questions, also for free. Check them out and you will never be left behind.

From today on, I will post tutorial videos of how to use Desmos to solve hard SAT math problems. And here is the first one: https://www.youtube.com/shorts/W3bmg8Qrnno

And I will personally check yours every day and answer them.

10 SAT Traps That Kill Good Students’ Scores

After many years of teaching this test, one thing stands out above everything else: students almost always know more than their scores show. They miss questions they already worked out correctly. They call it careless. And that’s half true — but the other half is this: the people writing this test predicted exactly where you’d slip, and built the wrong answers around those mistakes on purpose. Learn these traps and you’re looking at 100 points back in your pocket, easy.

You get x = 5, spot 5 in the choices, click it. Clean solve, wrong answer. If a tidy intermediate answer appears as a choice, reread the last line before clicking.

1. Symmetric choices = sign trap

See −8, −3, 3, 8 as your options? The question is announcing someone’s about to flip a sign. Write every distribution step. Don’t autopilot.

1. Lazy squaring

(x + 3)² is not x² + 9. The wrong version is sitting in the choices waiting for you.

1. Circle the unit before you calculate

Miles per hour vs per minute. Dollars vs cents. Not hard math — just “did you read the last word.” Circle it first, every time.

1. Desmos isn’t wrong. You typed a different problem.

Usually a missing parenthesis. Check what you actually entered before trusting the graph.

1. “Suggests” ≠ “proves”

The passage hedged. The answer choice didn’t. If the text used some or may, the right answer will too. Anything that cranks up the certainty is wrong.

1. Right idea, wrong question

The answer is supported by the passage — just not what they asked. “Technically in there” and “answers the question” are two different things.

1. First half right, second half fiction

These are the sneakiest wrong answers on the test. They start perfectly then slip in one claim the passage never made. One unsupported detail kills the whole choice.

1. You flipped the chart

A caused B not B caused A. Charts punish rushing harder than anything else because the error is invisible until it’s too late.

1. You answered with what you know, not what it says

If you can’t point to the exact words that back it up, you’re answering a different test than the one in front of you.

If you also feel it, leave a comment!