Express (7+ √5)/(3+√5) in the form a + b √5, where a and b are integers.

(7+ √5)/(3+√5)Here, the denominator is not rational - (numbers like 2 and 3 are rational). A number with an irrational denominator isn't incorrect, it just isn't in the simplest form it can be in.To rationalise the denominator in this case, we want to use the denominator's conjugate (e.g. Conjugate of 2-√3, would be 2+√3)We do this because it helps remove the surd from the denominator.(7+ √5)/(3+√5) * (3-√5) /(3-√5) (Note that the second part - (3-√5) /(3-√5) - we use this because anything divided by itself equals 1. Multiplying anything by 1 doesn't change it's value)Multiplying fractions (toptop and bottombottom): (7+ √5)(3-√5)/(3+√5)(3-√5) Use FOIL to multiply out brackets and simplify---> 4-√5So, a=4 and b=-1

OG
Answered by Oscar G. Further Mathematics tutor

19226 Views

See similar Further Mathematics GCSE tutors

Related Further Mathematics GCSE answers

All answers ▸

Factorise the following quadratic x^2 - 8 + 16


Why is it that when 'transformation A' is followed by 'transformation B', that the combined transformation is BA and not AB?


Solve the simultaneous equations xy=2 and y=3x+5.


How do I know I can multiply two matrices and if so, how do I do it?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning