14/08/2026
📘 **JOE BLESSING ACADEMIA** — Math Note 🧮
**TOPIC: SURDS**
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**A. WHAT IS A SURD?**
A surd is an irrational root that cannot be simplified to remove the root — e.g. √2, √3, √5, ∛7.
Note: √4 = 2 is **not** a surd (it simplifies to a whole number).
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**B. LAWS OF SURDS**
1️⃣ √a × √b = √(ab)
2️⃣ √a ÷ √b = √(a/b)
3️⃣ a√c ± b√c = (a±b)√c (like surds only)
4️⃣ √a × √a = a
5️⃣ (√a)² = a
**Example:**
Simplify: √8 + √18
= √(4×2) + √(9×2)
= 2√2 + 3√2
= 5√2
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**C. RATIONALIZING THE DENOMINATOR**
Rule: Multiply top and bottom by the **conjugate** of the denominator.
**Example 1:**
Rationalize: 1/√3
= (1×√3)/(√3×√3)
= √3/3
**Example 2:**
Rationalize: 1/(2+√3)
Multiply by conjugate (2−√3):
= (2−√3) / [(2+√3)(2−√3)]
= (2−√3) / (4−3)
= 2−√3
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**D. MULTIPLYING SURDS**
**Example:**
(√5 + √2)(√5 − √2)
= (√5)² − (√2)²
= 5 − 2 = 3
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**E. QUICK TIP**
Always simplify a surd first by breaking it into a **perfect square factor** × another factor.
E.g. √50 = √(25×2) = 5√2
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✏️ **Practice Question:**
Rationalize: 3/(√5 − √2)
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Want the next one to be Quadratic Equations, Simultaneous Equations, or a Surds/Indices/Logs mixed exam-style worksheet?