Simplify (7+sqrt(5))/(sqrt(5)-1), leaving the answer in the form a+b*sqrt(5)

Step 1 - Identify the difference between the required form of the answer and the expression to be simplified: 

It can be seen that in order to simplify the expression we need to somehow get rid of the denominator.

Step 2 - Attempt a method to get rid of the denominator: 

The best way to get rid of the denominator is to multiply it by (sqrt(5)+1). In order to keep the expression the same we must do the same to the numerator as well. 

This gives us,

((7+sqrt(5))/(sqrt(5)-1))*((sqrt(5)+1)/(sqrt(5)+1))

Step 3 - Carry out the necessary calculations:

The top parts of the fractions multiply together and the bottom parts of the fractions multiply together.

For the top part this gives us,

(7+sqrt(5))(sqrt(5)+1) = 7sqrt(5)+7+5+sqrt(5)

= 8*sqrt(5)+12

For the bottom part this gives us,

(sqrt(5)-1)*(sqrt(5)+1) = 5+sqrt(5)-sqrt(5)-1 = 4

Dividing the top part by the bottom part gives us,

2*sqrt(5)+3

Step 4 - Check that the answer is in the correct form.

The question asks for an answer in the form,

a+b*sqrt(5)

Our answer can be written in this format with a = 3 and b = 2.

Answered by Ian R. Maths tutor

18575 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Using partial fractions, find f(x) if f'(x)=5/(2x-1)(x-3)


f(x) = (4x + 1)/(x - 2) with x > 2. Find a value for 'x' such that f'(x) (first derivative of f(x) with respect to x) is equal to -1.


Find (dy/dx) of x^3 - x + y^3 = 6 + 2y^2 in terms of x and y


A circle A has equation x^2+y^2-6x-14y+54=0. Find a) the coordinates of the centre of A, b) the radius of the circle A.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences