I only need question 18 done. Look at the instructions for what to do.

For problems 15 -26 , use the change of variable technique to find an antiderivative in terms of x . 15. cos(4x) dx 16. 3x 4 , 11 e dx 17. x (5 + x dx x 'sin( x- ) dx sin(x) 18. 19. J dx 20. S cos(x) dx 2+ x