area between curves
1. Find the area between x=1 and x=3 for: f(x) = x+4 and
g(x)=1
2. Find the area between x =-1 and x=1 for: f(x) = 2-x^2 and
g(x) =3
3. find the area between: f(x) = x^2 and g(x) = 2x+3
4. find the area between: f(x) = 4-x^2 and g(x) =3x