The expression: sqrt ( 5 x² - 27 x + 10 ) A real number is a square root of a positive number. x 1/2 = ( 27 +/- sqrt ( 729- 200 )) / 10 x 1/2 = ( 27+/- 23 ) / 10 x 1 = 4/10 = 0.4 x 2 = 50/10 = 5 Answer: The expression is defined as a real number for: x ∈ ( - ∞, 0.4 ] ∪ [ 5, + ∞ ).