3.91=(2000e^(-0.8t))/((1+125e^(-0.8t))^2)
f(x)= {x-7}{\2x-9}
f(x)=x-2, -2<x<2
5/8 + 3/40 +7/10 +5/6
2Power[x,2]-x-21=0
ln(x)=-12.25
³√4÷√2
solve y''+y'+y=x^2
4/16*512
evaluate 573 + 30%
