IF U HELP ILL GIVE BRAINLIEST

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

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

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