Estimate the interval(s) on which the function is increasing and decreasing.f(x) = x4 - 12x2 + 35

Question

A. decreasing on (-?, -2.45)?(2.45, ?); 
increasing on (-2.45, 2.45)
B. decreasing on (-?, -2.65)?(-2.24, 2.24)?(2.65, ?);
increasing on (-2.65, -2.24)?(2.24, 2.65)
C. increasing on (-?, -2.45)?(0, 2.45);
decreasing on (-2.45, 0)?(2.45, ?)
D. decreasing on (-?, -2.45)?(0, 2.45);
increasing on (-2.45, 0)?(2.45, ?)

Answer 1

Answer: D