2 (x - 7) - x*(x + 7)
(x - 1*7)^2 - x*(x + 7)
1*(x - 7/3)
49 - 21*x
2 2 (-7 + x) - x - 7*x
(-7 + x)^2 - x^2 - 7*x
49.0*(-1 + 0.142857142857143*x)^2 - x*(7.0 + x)