What is it
A surd is an irrational root, like √2 or √7, left in exact root form rather than as a rounded decimal — GCSE Higher covers simplifying, adding, and rationalising the denominator of expressions involving surds.
Why it matters
Surds are the first place students meet the idea of keeping an answer exact rather than rounding — a mathematical habit that becomes essential at A-Level, where exact answers are expected by default.
Exam tip
To simplify a surd, look for the largest square number factor of the number under the root — spotting this factor quickly (rather than trying every square number in order) saves significant time.
Related topics
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