請問應該點樣計decreasing for x 0,請加以解釋THX

f(x) = (2x^2 +3)^(3/2)
f’(x) = (3/2) * (2x^2 +3)^(1/2) * (4x)
For x less than 0,
f’(x) is negative,
i.e. The slope of y = f(x) is negative
Hence, f(x) is decreasing for x less than 0.
For x greater than 0,
f’(x) is positve,
i.e. The slope of y = f(x) is positive
Hence, f(x) is increasing for x greater than 0.’