Hello, can u help please with these

21. Given f '(x) = 2sin*(2x) -3sin'(4x) , at which x-coordinate(s) below does the graph of f (x) change concavity over the interval (0, 2)? A. 1.938 B. 1.146 C. 0.667 D. 1.571 E. 0.56723. If 130') = 21'3 153'2 + 241' + l is the velocity function for a particle maving along the xaxis, for time 1' seconds, nd each of the following: a. when the particle changes direction for I 2 0. b. for what intervals of time {I Z l[1}the particle is moving to the left. c. for what intervals of time {I 2 0 }the particle has increasing speed. d. for what intervals of time {3' Z 0 }the acceleration of the particle is positive