12.1  d(pi*(10t)^2)/dt where t = 2.5

12.4  b) plot x^3/3 - 5x,4x-18,-1/4*x-21/4,  where x from -4 to 20  where y from -20 to 4
      d) plot 1/(x^2+1),x/2+1,-2x-3/2 where x from -2 to 1 where y from -1 to 2

12.5  a) plot x^2-2x,2x-4, where x from -4 to 4
      c) plot (2x-1)^3, -1/24*(x+1/2)-8, -1/24*(x-3/2)+8 where x=-10..10,y=-10..10
      d) plot x^4/2+1,4x+97/32, where x from -1 to 1

12.6  plot 2+1/x,4-x where x=0..4,y=0..4

12.8  plot sqrt(25-x^2), -3/4*x+25/4 where x=0..5,y=0..5 

12.9  a) monotonicity x^3-3x^2
      d) monotonicity x/ln x

12.10 a) points of inflection x^3-6x^2+12x+4
      b) points of inflection 3/(x-4)
      d) points of inflection x^2(lnx-0.5)
      e) points of inflection e^(-x^2)
      f) points of inflection x^3-6x^2

12.11 a) plot -arctan x -1
      b) plot 1/e-e^(-x)
      c) plot 1-arctan x
      d) Plot[Piecewise[{{-(x+1)^2*(x-2)/2, x < 0}, {(x/2-1)^3*(x/2+1)+2, x > 0}}], {x, -2, 3}]

12.12 b) plot[{8x^2-x^4, 16},{x,-4,4}]
      e) plot[{x*(ln x)^2, 4/e^2},{x,-1,2}]
      f) plot[{sqrt(2x^3+3x^2), 1},{x,-2,2}]
      g) plot x-arctan x
      x) plot[{ln(x^4+4x^3+30), ln 3},{x,-5,5}]
      y) Plot[Piecewise[{{ln -x, x < 0}, {ln x, x > 0}}], {x, -2, 2}]

12.13 a) plot[{x^2-2x+3, 2, 18},{x,0,5}]
      b) plot[{x^3-3x+1, -1, 19},{x,-2,3}]
      c) plot[{x-ln x, 1, e-1},{x,1/e,e}]
      d) plot[{arccos(x), pi},{x,-1,1}]
      e) plot[{e^(-x^2),1},{x,-3,3}]
      f) plot[{x/(1+x^2),1/2,-1/2},{x,-2,2}]
      roots x/(1+x^2)
      solve x/(1+x^2)> 0
      solve x/(1+x^2)< 0
      monotonicity x/(1+x^2)
      points of inflection x/(1+x^2)
      extrema x/(1+x^2)
      asymptotes x/(1+x^2)

12.14  plot[{4x(6-x)(4-x),640/27+sqrt(7)*448/27},{x,-1,10}]

12.15  Plot[{3p^2-35/4p^3, 64/1225}]

12.16  Plot[{1*x^2*(1-x), 4/27}]

Kruus    plot[{pi*x^2+2/x,3*(pi)^(1/3)},{x,-2,2}]

12.19 b) asymptotes x^2/(x^2-4)
      d) asymptotes (2x^2+1)/(x+1)
      f) asymptotes 2x-(cos x) / x

12.20 b) asymptotes (4x+4)/x^2
      f) asymptotes sqrt|x^2-2x|