What is the answer to this problem?

What is the equation of the following graph in vertex form? parabolic function going down from the left through the point zero comma twelve and through the point two comma zero and turning at the point four comma negative four and going up through the point six comma zero and continuing towards infinity courtesy of texas instruments a: y = (x − 4)2 − 4 b: y = (x + 4)2 − 4 c: y = (x + 2)2 + 6 d: y = (x + 2)2 + 12

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

Which of the following is the best first step in solving the equation below? 4+2㏒³x=17