i) Simplify (2 * sqrt(7))^2 ii) Find the value of ((2 * sqrt(7))^2 + 8)/(3 + sqrt(7)) in the form m + n * sqrt(7) where n and m are integers.

i) (2sqrt(7))2 = 2 sqrt(7)2 = 4 * 7 = 28      (1 mark) ii) First of all substitute the answer from above.    ((2 * sqrt(7))2 + 8) / (3 + sqrt(7)) = (28 + 8) / (3 + sqrt(7)) = 36 / (3 + sqrt(7)) Multiply by (3 - sqrt(7))/(3 - sqrt(7)) = 1.    36 / (3 + sqrt(7)) = 36 / (3 + sqrt(7)) * (3 - sqrt(7)) / (3 - sqrt(7)) = (36 * (3 - sqrt(7))) / ((3 + sqrt(7)) * (3-sqrt(7)) = (108 - 36 * sqrt(7)) / (9 + 3 * sqrt(7) - 3 * sqrt(7) - 7) = (108 - 36 * sqrt(7)) / 2 = 54 - 18 * sqrt(7).      (3 marks) (Hence m=54 and n=-18) 

Answered by Andrew B. Maths tutor

6707 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

A car is moving on an inclined road with friction acting upon it. When it is moving up the road at a speed v the engine is working at power 3P and when it is moving down the road at v the engine is working at a power P. Find the value of P.


Prove algebraically that the sum of the squares of two consecutive multiples of 5 is not a multiple of 10.


A curve has the equation x^2 +2x(y)^2 + y =4 . Find the expression dy/dx in terms of x and y [6]


I don’t think I’m smart enough for this course, should I drop it?


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