Algebra: Expressions, Equations and Exponents
Variables in equations and inequalities, the exponent rules, absolute value and the algebraic word problems E3n lists under Algebra, Geometry and Other Math.
9 topics · 37 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Variables, Expressions and Substitution
- How it worksHow does substituting a value for x collapse a whole expression down to one number?
- Worked exampleFind the value of 3a² - 2ab when a = -2 and b = 5.
- Worked exampleWalk me through a made-up operation where a # b means 2a + 3b, and find 4 # 5.
- Common mistakeWhy isn't 3x the same thing as x³ when both are built from a 3 and an x?
Like Terms and the Distributive Property
- How it worksHow does distributing a 5 across (x + 7) hand that 5 to both terms and not just the first?
- Worked exampleFind the simplified form of 4(2x - 3) - 2(x - 5).
- Common mistakeWhy doesn't -(x - 4) simplify down to -x - 4?
Solving Linear Equations in One Variable
- How it worksHow does undoing an equation in the reverse of the order of operations strand x by itself?
- Worked exampleWalk me through solving 5(x - 3) = 2x + 9 the way the SSAT wants it done in under a minute.
- Common mistakeWhy doesn't a term keep its original sign when it crosses the equals sign?
- Worked exampleFind x when (x + 4)/3 = 7 - x.
- Going furtherWhat happens when solving an equation ends in 5 = 5, and what happens when it ends in 5 = 7?
Inequalities and When the Sign Flips
- How it worksHow does multiplying both sides by a negative number spin the inequality symbol around?
- Worked exampleFind every value of x satisfying -3x + 5 > 14 and shade them on a number line.
- Common mistakeWhy isn't x > 4 the same shaded stretch of the number line as 4 > x?
- Going furtherWhat changes about the solution set when x is also required to be a whole number?
Properties of Exponents
- How it worksHow do the repeated factors on the top and bottom of x⁵/x² literally cancel away to leave x³?
- Common mistakeWhy isn't x² + x³ equal to x⁵ when x² times x³ certainly is?
- Worked exampleFind the value of (2³ × 2⁵) ÷ 2⁶ without working out any of those powers separately.
- Worked exampleWalk me through simplifying (3x²y)³ so that every factor inside the parentheses gets cubed.
- Going furtherWhat do a zero exponent and a negative exponent mean once the cancelling picture is in front of you?
Square Roots and Perfect Squares
- How it worksHow does pulling perfect squares out of the root of 72 turn it into 6 times the root of 2?
- Worked exampleFind the root of 144 plus the root of 25 minus the root of 81 using squares you know by heart.
- Worked exampleWalk me through estimating the square root of 50 to the nearest tenth with no calculator.
Absolute Value
- How it worksHow does reading the bars around x as distance from zero explain why the result is never negative?
- Worked exampleFind both solutions of the equation with 8 as the absolute value of x - 3, by walking 8 units each way.
- Worked exampleFind the value of the absolute value of 3 - 11, plus that of -5, minus that of 2 - 2.
- Going furtherWhat does a solution set of numbers less than 5 units from zero look like as a stretch of number line?
- Common mistakeWhy isn't the absolute value of a sum always equal to the sum of the two absolute values?
Algebraic Word Problems
- How it worksHow does five less than three times a number become 3n - 5 and never 5 - 3n?
- Worked exampleWalk me through a problem where Maya is 4 years older than Sam and their ages add to 38.
- Worked exampleFind the two consecutive even integers that add up to 74.
- Worked exampleFind how many dimes there are when 20 dimes and quarters together are worth 3.65 in dollars.
- Common mistakeWhy doesn't the quotient of 8 and x mean x divided by 8?
Two Equations, Two Unknowns
- How it worksHow does adding two equations together make one of the variables vanish outright?
- Worked exampleFind x and y when x + y = 14 and x - y = 4.
- Worked exampleWalk me through solving 2a + 3b = 19 together with a = b + 2 by substitution.
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