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


8.2	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

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

8.6	c) d(2/r^5+3*pi\2)/dr
	e) d(x*e^x)/dx
	f) d(sqrt(6u/(1+2u)))/du

8.7	b) d(0.02*(x^2+2x)^3)/dx where x = 7
	d) d(0.06*(x*sqrt(1+4x)))/dx where x = 12
	f) d(pi/180*(tan x))/dx
	
8.11	d(0.0012*4/3*pi*x^3)/dx where x = 3.5
	4/3*pi*(3.5012)^3-4/3*pi*(3.5)^3

8.13	b) d(4x-0.07*(sqrt(x)))/dx where x = 16
	sqrt(15.93)
	c) d(3^5*x+0.02*(x^5))/dx where x = 3
	3.02^5
	d) d(sin(pi/4)*x+pi/180*(sin (x)))/dx where x = pi/4
	sin(46*pi/180)
	e) d(x+1*(ln(x)/ln(10)))/dx where x = 10
	ln(11)/ln(10)
	
8.15	d((300/(0.0005*50^2+2)-50) * x + d*300/(0.0005x^2+2)-50)/dx where x = 50
	d((300/(0.0005*50^2+2)-50) * x -5*300/(0.0005x^2+2)-50)/dx where x = 50
	300/(0.0005x^2+2)-50 where x = 45