What is the area of a circle if the circumference is 31.4 inches ?

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

Find the directions in which the function increases and decreases most rapidly at upper p 0p0. then find the derivatives of the function in these directions. f(x,y)equals=x squared plus xy plus y squaredx2+xy+y2, upper p 0p0left parenthesis 1 comma negative 4 right parenthesis