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

18140 Views

See similar Further Mathematics GCSE tutors

Related Further Mathematics GCSE answers

All answers ▸

Prove that tan^2(x)=1/(cos^2(x))-1


Work out the gradient of the curve y=x^3(x-3) at the point (3,17)


The equation of the line L1 is y = 3x – 2 The equation of the line L2 is 3y – 9x + 5 = 0 Show that these two lines are parallel.


Why does the discriminant b^2-4ac determine the number of roots of the quadratic equation ax^2+bx+c=0?


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:

© 2025 by IXL Learning