Arubber band is n inches long. If a child stretches the rubber band, and a new length of the rubber band is 1.36n, what percentage did it increase. And please tell me how you did it ! I REALLY NEED HELP

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