Exponents, Equations & Inequalities
We revise and extend the laws of exponents to rational exponents, then solve every type of equation met in Grade 10: linear, quadratic (by factorisation), simultaneous, and literal. We close by solving linear inequalities and displaying the solution on a number line.
2.1 Laws of Exponents
- Revise laws of exponents for integer exponents ($m,n\in\mathbb{Z}$)
- Use the laws for rational exponents ($m,n\in\mathbb{Q}$)
- Simplify and solve exponential expressions
Real-World Connection
Every memory card, hard drive, and phone plan is measured in powers of 2: 4 GB, 8 GB, 16 GB, 32 GBโฆ When engineers combine two memory banks of $2^{10}$ bytes each, they know instantly: $2^{10}\times2^{10}=2^{20}$ bytes = 1 MB. The exponent law $a^m\cdot a^n=a^{m+n}$ is not an abstract rule โ it is why all digital technology uses base-2 storage.
Product rule
Same base; add exponents.
Quotient rule
Same base; subtract exponents.
Power of a power
Multiply exponents.
Power of a product
Distribute exponent over the product.
Negative exponent
Reciprocate; make exponent positive.
Zero exponent
Any non-zero base to power 0 equals 1.
Rational exponent
Denominator = root index; numerator = power.
๐จ Common Mistake
but . The base of an exponent is only what is in brackets. When in doubt, add brackets.
Worked Example
Simplify using exponent laws
Problem
Worked Example
Rational Exponents
Problem
CAPS Cognitive Level Distribution
2.2 Equations
- Revise and solve linear equations
- Solve quadratic equations by factorisation
- Solve simultaneous linear equations in two unknowns
- Solve literal equations (changing the subject)
- Solve word problems involving linear, quadratic or simultaneous equations
Real-World Connection
A pharmacist mixing a solution needs an exact concentration โ too much or too little and the medicine is wrong. The equation $2x+15=63$ is that precise constraint: $x$ is the unknown volume and the equation says the total must be exactly 63 ml. Solving it finds the one measurement that satisfies the prescription โ and any method is valid as long as you treat both sides of the scale equally.
Property / Rule
Zero Product Property
If a product equals zero, at least one factor must be zero. This is the foundation for solving quadratic equations by factorisation.
Property / Rule
Solving simultaneous linear equations
Substitution: express one variable in terms of the other from one equation, then substitute into the second. Elimination: make coefficients of one variable equal and subtract (or add) the equations.
Property / Rule
Literal equations (changing the subject)
Use the same algebraic operations as solving any equation, but the answer will be in terms of other letters rather than numbers.
๐จ Common Mistake
ALWAYS rearrange a quadratic to standard form BEFORE factorising. Never divide both sides by โ this loses the solution .
Worked Example
Solve a quadratic by factorisation
Problem
Worked Example
Simultaneous linear equations
Problem
Worked Example
Literal equation โ changing the subject
Problem
Worked Example
Word problem โ setting up and solving an equation
Problem
CAPS Cognitive Level Distribution
2.3 Linear Inequalities
- Solve linear inequalities and show the solution graphically on a number line
- Work with compound inequalities (AND/OR)
- Express solutions using interval notation
Real-World Connection
An inequality is not a single answer but a region of answers. 'You must be taller than 1ยท5 m to ride this attraction' is an inequality โ it describes all heights above 1ยท5 m, not one specific height.
Property / Rule
Inequality Rules
You can add/subtract the same quantity on both sides. Multiplying or dividing by a POSITIVE number preserves the direction. Multiplying or dividing by a NEGATIVE number REVERSES the direction.
Property / Rule
Number line and interval notation
Open circle โ at an endpoint means that value is EXCLUDED ( or ). Closed circle โ means INCLUDED ( or ). Interval notation: round bracket for excluded, square bracket for included.
๐จ Common Mistake
THE most common error: forgetting to flip the sign when multiplying or dividing by a negative number. does NOT give ; it gives .
Worked Example
Compound inequality
Problem
CAPS Cognitive Level Distribution