SAT Math | Tips & Summaries

This resource will cover common concepts that you should know to attempt the SAT Math section. If anything was missed in this resource, feel free to contact me @scripted_mari0 on discord or join the StudyHaven discord server.

Quadratics


(x+y)(xy)=x2y2(x+y)(x-y) = x^2 - y^2 (x+y)2=x2+2xy+y2(x+y)^2 = x^2 + 2xy + y^2 (xy)2=x22xy+y2(x-y)^2 = x^2 - 2xy + y^2

Sometimes you'll be asked to solve for the sum or the product of the roots of a quadratic equation. You can use the quadratic formula and then add or multiply the results, but it's quicker to just memorize these two expressions.

sum of the roots: ba-\frac{b}{a}
product of the roots: ca\frac{c}{a}

The discriminant, DD, of a quadratic in the standard form ax2+bx+c=0ax^2 + bx + c = 0 is b24acb^2 - 4ac

  • If the discriminant is positive, the quadratic has 2 real solutions.
  • If the discriminant equals 0, the quadratic has 1 real solution.
  • If the discriminant equals negative, the quadratic has no real solutions.

Key Points
  • The standard form of a parabola is y=ax2+bx+cy = ax^2 + bx + c, where cc is the yy-intercept. If aa is positive, the parabola opens up, and if aa is negative, it opens down.



Logarithms (Exponential growth and decay)


General equation of exponential growth or decay:
c=abtc = ab^t
Where:

  • cc = final amount
  • aa = original amount
  • bb = multiplier
  • tt = number of changes

Example
The number of trees in a forest double every year. Find the number of trees after 3 years if the number of trees was 20 initially.

20×2320\times 2^3 where 20 is the original amount, 2 is the multiplier (doubles every year) and 3 is the number of changes (changes every year for 3 years)



Linear Algebra


The equation of a line can take two forms. In either form, (x,y)(x, y) is a point on the line.

  • In slope-intercept form, y=mx+by = mx+b, the slope is mm and the yy-intercept is bb.
  • In standard form, Ax+By=CAx+By = C, the slope is AB-\frac{A}{B} and the yy-intercept is CB\frac{C}{B}

Another equation for a line is yy1=m(xx1)y - y_1 = m(x - x_1)

Given two points on a line, (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2), the slope is (y2y1)(x2x1)\frac{(y_2 - y_1)}{(x_2 - x_1)}

Key Points
  • Two linear equations with infinitely many solutions represent the same line.
  • Parallel lines have the same slopes and no points of intersection.
  • Perpendicular lines have slopes that are negative reciprocals and intersect at a right angle.
  • To find a point of intersection, plug the points into both equations to see if it works, or graph the lines on your calculator.



Coordinate Geometry


There are 4 different forms for a circle equation:

  • The standard form
  • The general form
  • The polar form
  • The parametric form

The SAT only considers the standard form and the general form.

The standard form of a circle equation is (xh)2+(yk)2=r2(x-h)^2 + (y-k)^2 = r^2, where (h,k)(h, k) is the center and rr is the radius.

The general form of a circle equation is x2+y2+2gx+2fy+c=0x^2 + y^2 + 2gx + 2fy + c = 0 where gg, ff and cc are constants.

To convert the general form equation to the standard form equation, remember that the center is (g,f)(-g, -f) and the radius is g2+f2c\sqrt{g^2 + f^2 - c}

Key Points
  • The general form equation is just an expanded version of the standard form.
  • Most graphing calculators have a separate mode for plotting circle equations called conic mode. Instead of having to switch to this mode, rely on desmos where you can just enter the equation.
  • To find the slope of a line that passes through the middle and also passes through a point, first find the slope of the tangent to the circle at the point and get the reciprocal of the slope.


Geometry and Trigonometry


Basic trigonometric rules:

sin(θ)=oppositehypotenusesin(\theta) = \frac{opposite}{hypotenuse} \\ cos(θ)=adjacenthypotenusecos(\theta) = \frac{adjacent}{hypotenuse} \\ tan(θ)=oppositeadjacenttan(\theta) = \frac{opposite}{adjacent}

The sine rule:

sinAa=sinBb=sinCc\frac{sin A}{a} = \frac{sin B}{b} = \frac{sin C}{c}

The cosine rule:

c2=a2+b22ab cosCc^2 = a^2 + b^2 - 2ab\space cosC

Heron's formula:

A=s(sa)(sb)(sc)A = \sqrt{s(s-a)(s-b)(s-c)}

Area of a triangle:

A=12ab sin(θ)A = \frac{1}{2}ab\space sin(\theta)

Where (For area of a triangle and Heron's formula):

  • AA = area of the triangle
  • ss = half perimeter of the triangle
  • aa, bb, cc = sides of the triangle
  • θ\theta = angle

Key Points
  • The sum of interior angles of a triangle is 180°180\degree

  • The sum of two interior angles of a trianglel is equal to the opposite exterior angle.

  • The sum of interior angles of a quadrilateral is 360°360\degree

  • If a question is based on radians, make sure to only give an answer that is in radians unless the question states otherwise. The same goes for degrees.


A Simple Guide



RTFQ - The final question will start with something like "Which of the following," "What is," or "How many." Find the final question (it's usually at the end) and write down key words. If the question asks for the value of a variable or the measure of an angle, write down which variable or which angle. If it asks for a specific part of a graph or a word problem, write down which part. Terms and units, such as median, positive, minutes, or miles, also go on the scratch paper.

Let the answers point the way - On multiple-choice questions, the answer type often gives a clue about how to approach the question. Do the answers have numbers? variables? equations? graphs? a bunch of words? Use that information to get started.

Work in bite-sized pieces - Rather than trying to plan the entire question up front, just get started. Work the question one bite-sized piece at a time, reading more along the way and making notes on the scratch paper. The final question and the answer types usually reveal the best approach. If it's not obvious, either mark the question to come back to later or enter your Letter of the Day.

Use POE - On some questions, it's possible to eliminate answers along the way while working in bite-sized pieces. If the question asks about an equation representing a situation, for example, an answer that gets any piece of the equation wrong can be eliminated. Eliminate answers that don't work.



❗Some points in this post are from the princeton review guide❗

Credits for some points in this post goes to @vpurnitha on discord

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