Pow(base,exponent)=(base)^(exponent).
Expression becomes:
(5+2sqrt(6))^(x^2-3)+(5-2sqrt(6))^(x^2-3)=10
Note that 5+5=10, so if the sqrt term can be removed we have a solution. If x^2-3=1, so x^2=4 and x=+2, the sqrt terms cancel out, so we're left with 5+5=10! Therefore the solution is x=2 or -2.