(5/3)x^2 - 5 = 0 has the coefficients a=5/3, b=0 and c = -5.
Thus, the quadratic formula would be appropriate here:
-0 plus or minus sqrt(0^2 - 4(5/3)(-5) ) x = ------------------------------------------------------- 2(5/3) plus or minus sqrt(100/3) = ------------------------------------ 10/3 3 10 = ------* ----------- = sqrt(3) (answer) 10 sqrt(3)