Fiche de révision : Mastering Scientific Notation and Algebraic Expansion

📋 Course Outline

1. Scientific notation and index laws
2. Algebraic expressions and expansion

📖 1. Scientific notation and index laws

🔑 Key Concepts & Definitions

• Scientific notation : Scientific notation represents a number as $a\times10^n$ where $1\le|a|<10$ and $n$ is an integer.
• Index laws : Index laws are rules for simplifying powers with the same base, or powers in fractions and products.
• Negative indices : Negative indices mean a power with exponent $-n$ is the reciprocal of the same base to exponent $n$.

📝 Essential Points

• Division law: $\frac{a^m}{a^n}=a^{m-n}$ for $a\ne0$.
• Zero index: $a^0=1$ for $a\ne0$.
• Raising a power to a power: $(a^m)^n=a^{mn}$.
• For $a\ne0$, $a^{-n}=\frac{1}{a^n}$.

💡 Memory Hook

Division subtracts indices: top exponent minus bottom exponent.

📖 2. Algebraic expressions and expansion

🔑 Key Concepts & Definitions

• Pronumerals : Pronumerals are letters used to represent unknown values in algebraic expressions and equations.
• Distributive laws : Distributive laws let you multiply a single term across a sum or difference inside brackets.
• Binomial expansions : Binomial expansion rewrites $(a+b)^n$ into a sum of terms involving powers of $a$ and $b$.

📝 Essential Points

• Distributive law: $x(a+b)=xa+xb$ and $x(a-b)=xa-xb$.
• FOIL for $(a+b)(c+d)$ gives first, outside, inside, last: $ac+ad+bc+bd$.
• Quadratic trinomial form $ax^2+bx+c$ can be expanded by distributing and then combining like terms.

💡 Memory Hook

FOIL order: First–Outside–Inside–Last.

⚠️ Common Pitfalls & Confusions

1. Students often think $a^0=a$ instead of using $a^0=1$ for $a\ne0$.
2. Students may add indices when dividing powers instead of subtracting them.
3. Students sometimes treat $a^{-n}$ as $(-a)^n$ rather than the reciprocal $1/a^n$.
4. Students may distribute incorrectly by skipping a sign when expanding $(a-b)$.
5. Students often forget an entire FOIL term when multiplying two binomials.
6. Students may expand brackets but fail to combine like terms in quadratic expressions.

✅ Exam Checklist

1. Convert a number to scientific notation of the form $a\times10^n$ with $1\le|a|<10$.
2. Simplify expressions using the division law $\frac{a^m}{a^n}=a^{m-n}$.
3. Simplify expressions using the zero index rule $a^0=1$ for $a\ne0$.
4. Simplify expressions using the power-to-a-power rule $(a^m)^n=a^{mn}$.
5. Rewrite expressions with negative indices using $a^{-n}=\frac{1}{a^n}$ for $a\ne0$.
6. Use pronumerals correctly in algebraic expressions to represent unknowns.
7. Expand products of terms using distributive laws over sums and differences.
8. Use FOIL to expand $(a+b)(c+d)$ into $ac+ad+bc+bd$.
9. Recognize and expand binomial expressions into an algebraic sum.
10. Expand and simplify a quadratic trinomial expression by distributing and combining like terms.