Question

Hi I do not how to simplify the problem

x^2 =40+12sqrt2

what would be x? BTW if you sqrt both sides it would be double square root so what then? how to simplify?

Answer 1

12 sqrt 2 = x^2 - 40
144 (2) = x^4 -80 x^2 + 1600
x^4 - 80 x^2 + 1312 = 0
graph to find zeros
http://mathportal.org/calculators/polynomials-solvers/polynomial-graphing-calculator.php

zeros at
x = -7.55, -4.80 + 4.80, +7.55
check those in original
+ and - 7.55 works
the 4.8 does not