Surd Calculations?

Surds are numbers left in 'square root form' (or 'cube root form' etc). They are therefore irrational numbers. Surds are the root of numbers and not whole numbers.

Multiplication

square root of ab = square root of a x square root of b

square root of a x square root of a = a

Example: 

√2 × √6 = √12 (= 2× 6)

= √4 × √3

= 2√3

Addition and Subtraction

4√3 - 2√3 = 2√3

5√5 + 8√5 = 13√5

Note: 5√7 + 3√3 cannot be manipulated because the surds are different (one is √7 and one is √3)

Example:

Simplify √12 + √27

12 = 3 × 4. So √12 = √(3 × 4) = √3 × √4 = 2 × √3.

Similarly, √27 = 3√3.

Hence √12 + √27 = 2√3 + 3√3 = 5√3

 

 

 

NB

Related Maths GCSE answers

All answers ▸

Find the values of k for which the equation (2k-3)x^2- kx+(k-1)=0 has equal roots.


How do I make x the subject of the formula?


Show that (x+1)(x+2)(x+3) can be written as ax^3+bx^2+cx+d


Factorise 3x^2 + 15x