Rationalising the Denominator

Rationalising the denominator removes a surd from the bottom of a fraction, giving a rational denominator. For $\frac{1}{\sqrt{a}}$ we multiply top and bottom by $\sqrt{a}$; for $\frac{1}{a+\sqrt{b}}$ we multiply by the conjugate $a-\sqrt{b}$.

The value is unchanged, only the form is tidier.

You meet Rationalising the Denominator in the Indices, Surds and Logarithms chapter of SPM Additional Mathematics. Knowing the term precisely matters in the exam: questions often hinge on reading a keyword correctly, and because SPM marking is analytic, using the right definition in your working helps secure method marks.

Our teachers make sure a student can not only recite what Rationalising the Denominator means but use it fluently in a full solution.

Because the SPM Add Math paper is bilingual (BM/EN), it helps to know this term in each language: Rationalising the Denominator (EN) · Pemerasionalan Penyebut (BM) · 分母有理化 (中文)

Other key terms from the Indices, Surds and Logarithms chapter you may want to check:

• Index
• Laws of Indices
• Surd
• Logarithm
• Laws of Logarithms
• Change of Base Formula