8.1     a) plot sqrt(x), x^2
        b) plot -sqrt(x), x^2
        c) plot log(x-1), 10^x+1
        d) plot 2-10^(x-1) , 1+log|x-2|
        c) plot 3*sin(2*x) where x from -pi/4 to 0
        f) plot 1+arccos(1-x) plot 1-cos(x-1) where x from 1 to pi +1

8.2     a) plot 3x-2 
        b) plot 2^x
        c) plot x^2
        d) plot x^2, x=0..1
        e) plot x^3
        f) plot sin x

8.3     a) Plot[y= x-5+ln(x-5)]
           ParametricPlot[{t+5},{t+ln t}]
        b) Plot[x= ln(y)^5+ln(y), y=0..10] 
           ParametricPlot[{e^t},{t^5+t},x=0..10]

8.4     a) Plot[x = ln(y-sin x)], Plot{y=e^x+sin x}
        b) Plot[y^2-2xy+x^2-4=0], Plot{y=-2+x}, Plot{y=2+x}

8.6     300*1.03^10

8.7     -ln(6.2)/ln(0.875)

8.8     a) e^(5*ln x) - x^5
        b) (ln(1/e^(3x)) - (-3x)
        c) e^(3/2*ln 9) - 27
        d) (4ln(sqrt(x))+6ln(x^(1/3))) - ln x^4
        e) 16^(log_2(48^(1/4))-1) - 3
        f) e^(2ln(cos(x)))+(ln(e^sin(x)))^2 - 1
        g) -log_8(log_4(log_2 16))
        h) log(log(sqrt(10^(1/5)))) - (-1)

8.9     a) 5log_5(25)+8log_2(64)-4log_3(27)+log_2(2)+log_5(1) - 47
        b) 3^(1-log_3(7))+5^(log_5(8)+1)-2.4^(log_(2.4)10+1) - (16+3/7)
        c) log_2(12) + log_2(25)/3+2log_2(4)/5-log_2(2^7)
        d) 4*(81^(1/4-1/2*log_9(4))+25^log_125(8)) - 19

8.15     -5/4*ln(1.5/4999)
        5000/(1+4999*e^(-0.8t)) where t= 10,11
        plot 5000/(1+4999*e^(-0.8t)) where t from 0 to 20