Algebraic Fractions

邊玩邊學

回答這些題目賺取能量，接著就能釣魚、探索。不需要帳號。

給老師：為 Algebraic Fractions（Maths [CIE]、Extended）準備好可直接使用的課程投影片, 複習筆記——用於你的課程，或把這個主題當成互動班級活動，讓學生以即時遊戲的方式進行。

課程筆記

Simplifying Algebraic Fractions

Factorise numerator and denominator fully.
Cancel any common factors (single term or bracket).
Cannot cancel a factor unless it is common to all terms in numerator/denominator.
E.g. \frac{6x}{x+1} cannot be simplified.
Always check if numerator factorises after simplification.

Adding & Subtracting Algebraic Fractions

Find the lowest common denominator (LCD).
LCD may be product of denominators, e.g. (x+2)(x+5).
If denominators share a factor, LCD is the LCM, e.g. \frac{1}{x} and \frac{1}{2x} have LCD 2x.
Rewrite each fraction over the LCD, multiplying numerator accordingly.
Combine into a single fraction and simplify numerator.
Check if numerator factorises for further cancellation.

Multiplying Algebraic Fractions

Factorise all numerators and denominators first.
Cancel any common factors between any numerator and any denominator.
Multiply numerators together and denominators together.
Check for further simplification.

Dividing Algebraic Fractions

Flip the second fraction (find its reciprocal) and change ÷ to ×.
Then follow the rules for multiplying algebraic fractions.
E.g. \frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}.

Solving Equations with Algebraic Fractions

Method 1: Combine fractions into a single fraction, then cross-multiply and solve.
Method 2: Multiply every term by each denominator to clear fractions.
Use brackets when multiplying by algebraic expressions.
Solve the resulting polynomial equation (often quadratic).

Common Mistakes & Tips

Always factorise before cancelling or adding fractions.
When subtracting, be careful with negative signs across brackets.
Check for difference of two squares (e.g. x²-25).
Leave answer in factorised form to see if cancellation is possible.

投影片

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

免費註冊登入

練習題

免費預覽——42 題中的 8 題。註冊即可查看全部。

1.Simplify \frac{5}{3x} \times \frac{9x}{20}.
Easy
- A\frac{3}{4}
- B\frac{45x²}{60x}
- C\frac{3x}{4}
- D\frac{45}{60}
2.Simplify \frac{x²+5x}{x²-25}.
Medium
- A\frac{x}{x-5}
- B\frac{x+5}{x-5}
- C\frac{x}{x+5}
- D\frac{x+5}{x+5}
3.Simplify \frac{x²-25}{x²-2x-35}.
Medium
- A\frac{x-5}{x-7}
- B\frac{x+5}{x+7}
- C\frac{x-5}{x+7}
- D\frac{x+5}{x-7}
4.Simplify \frac{5p²-20}{p} \div \frac{2p²-32}{p}.
Medium
- A\frac{5}{2}
- B\frac{5(p²-4)}{2(p²-16)}
- C\frac{5(p-2)}{2(p-4)}
- D\frac{5(p+2)}{2(p+4)}
5.Write \frac{x-5}{3} + \frac{6}{x+2} as a single fraction in its simplest form.
Medium
- A\frac{x²-3x-10+18}{3(x+2)}
- B\frac{x²-3x-10}{3(x+2)}
- C\frac{x²-3x+8}{3(x+2)}
- D\frac{x²-3x-10+6}{3(x+2)}
6.Simplify \frac{p}{2q} \times \frac{4pq}{t}.
Easy
- A\frac{2p²}{t}
- B\frac{4p²q}{2qt}
- C\frac{2p²q}{t}
- D\frac{4p²}{t}
7.Simplify \frac{ab-b²}{a²-b²}.
Medium
- A\frac{b}{a+b}
- B\frac{b}{a-b}
- C\frac{a-b}{a+b}
- D\frac{a}{a+b}
8.Simplify \frac{x²-5x}{2x²-50}.
Medium
- A\frac{x}{2(x+5)}
- B\frac{x}{2(x-5)}
- C\frac{x-5}{2(x+5)}
- D\frac{x}{2x+10}

複習筆記

## Algebraic Fractions - Night Before Exam Summary ### Simplifying - **Factorise** numerator and denominator fully. - **Cancel** common factors (single term or bracket). - Example: \(\frac{4x+6}{2x^2-7x-15} = \frac{2(2x+3)}{(2x+3)(x-5)} = \frac{2}{x-5}\) ### Adding & Subtracting 1. Find **lowest common denominator (LCD)**. 2. Write each fraction over LCD. 3. Combine numerators, simplify. 4. Check if final fraction can be simplified. - Example: \(\frac{x}{x+4} - \frac{3}{x-1} = \frac{x(x-1)-3(x+4)}{(x+4)(x-1)} = \frac{x^2-4x-12}{(x+4)(x-1)} = \frac{(x+2)(x-6)}{(x+4)(x-1)}\) ### Multiplying 1. Factorise all numerators and denominators. 2. Cancel common factors across fractions. 3. Multiply tops together, bottoms together. - Example: \(\frac{x}{3x+6} \times \frac{2x+4}{x+7} = \frac{x}{3(x+2)} \times \frac{2(x+2)}{x+7} = \frac{2x}{3(x+7)}\) ### Dividing - Flip the second fraction (reciprocal) and multiply. - Then follow multiplication steps. - Example: \(\frac{x+3}{x-4} \div \frac{2x+6}{x^2-16} = \frac{x+3}{x-4} \times \frac{(x-4)(x+4)}{2(x+3)} = \frac{x+4}{2}\) ### Solving Equations **Method 1:** Combine fractions into a single fraction, then cross-multiply and solve. **Method 2:** Multiply every term by all denominators to clear fractions, then solve. - Example: \(\frac{4}{x-3} + \frac{5}{x+1} = 5\) → multiply by \((x-3)(x+1)\) → \(4(x+1)+5(x-3)=5(x-3)(x+1)\) → solve quadratic. ### Key Tips - Always factorise first. - Watch for difference of two squares: \(a^2-b^2 = (a-b)(a+b)\). - Be careful with negative signs when subtracting. - Check if final answer can be simplified further.

Algebraic fraction: A fraction with an algebraic expression in the numerator and/or denominator.
Lowest common denominator (LCD): The smallest expression that is a multiple of all denominators in a set of fractions.
Reciprocal: The fraction obtained by swapping the numerator and denominator; used for division.
Factorising: Writing an expression as a product of its factors (e.g., common factor, quadratic factorisation, difference of two squares).
Cross-multiplying: Multiplying both sides of an equation by the denominators to eliminate fractions.

Unlock all 42 questions & more

建立免費帳號，即可查看這個主題的所有題目、投影片、字卡與複習筆記。

免費註冊登入

歷屆試題

這個主題的歷屆試題練習即將推出。

即將推出