Someone help me please

Can someone pls ! pls answer all. no explanation needed..

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle.he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field